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Bones  in  the  hand  and  wrist. 
(From  an  X  ray  [jhotograiJli.J 


APPLIED    PHYSIOLOGY 


I>XLL'DING 


THE    EFFECTS    OF   ALCOHOL 
AND    NARCOTICS 


BY 


FRANK   OVERTON,  A.M.,  M.D. 

LATE  HOUSE  SURGEON   TO  THE   CITY   HOSPITAL,   NEW  YORK 


ADVANCED    GRADE 


-j::*kc 


NEW   YORK  • :  •  CINCINNATI  • :  •  CHICAGO 

AMERICAN    BOOK    COMPANY 


Copyright,  1897,  by 
AMERICAN   BOOK  COMPANY 


APPLIED    PHYSIOLOGY 
E-P     29 


PREFACE 

This  text-book  of  Applied  Physiology  was  suggested  by 
a  series  of  popular  lectures  in  which  the  author  presented 
the  essential  principles  of  physiology  about  which  a  physi- 
cian is  consulted  daily.  His  explanations  of  many  common 
facts  were  entirely  novel  to  the  auditors,  and  on  investiga- 
tion it  was  found  that  the  school  text-books  were  silent 
upon  many  of  these  points,  especially  in  regard  to  the  cells, 
where  the  essential  vital  functions  of  the  body  are  carried 
on.  Throughout  this  book  the  fact  that  the  cells  are  the 
units  in  which  life  exists  and  acts  is  emphasized. 

The  author  has  endeavored  to  include  all  the  useful 
points  of  the  older  text-books,  and  to  add  such  new  matter 
as  the  recent  progress  of  physiological  and  hygienic 
science  demands.  He  has  avoided  technical  terms,  and 
has  sought  to  express  the  truths  in  simple  language  such 
as  he  would  use  in  instructing  a  mother  as  to  the  nature 
of  the  sickness  of  her  child. 

The  subject  of  alcohol  is  discussed  in  all  its  aspects. 
Its  evil  effects  are  not  exaggerated ;  but  the  alleged 
good  from  the  use  of  strong  drink  is  contrasted  with  its 
dangers  in  a  judicial  manner,  which  appeals  to  men  far 
more  effectively  than  dogmatic  abuse.  The  relation  of 
alcoholic  indulgence  to  other  forms  of  intemperance,  as 
excessive  sugar  eating,  is  also  explained. 

The  essential  act  of  respiration  is  oxidation  within  the 
cells.     The  relation  of  oxidation  to  the  disappearance  of 


6  PREFACE 

food,  to  the  production  of  waste  matters,  and  to  the 
development  of  heat  and  force,  is  dwelt  upon  throughout 
the  book. 

Many  of  the  demonstrations  at  the  ends  of  chapters  are 
new.  All  can  be  performed  without  the  purchase  of  a 
single  article  of  apparatus,  except  a  microscope.  The 
prepared  microscopic  specimens  can  be  borrowed  from  a 
physician. 

Most  of  the  cuts  are  entirely  new,  and  have  been 
sketched  by  the  author  from  actual  specimens.  The 
microscopic  appearances  of  the  tissues  are  especially  illus- 
trated. In  each  cut  the  illustration  of  a  point,  rather  than 
artistic  effect,  has  been  the  end  in  view. 

The  chapter  on  Repair  of  Injuries  is  an  entirely  new 
feature  in  a  school  text-book.  How  the  body  restores 
its  natural  functions  after  injury  is  as  practical  and  simple 
a  subject  as  how  it  sustains  itself  in  health. 

The  author  wishes  to  express  his  gratitude  to  his  friend 
and  instructor,  Professor  William  H.  Porter,  of  the  New 
York  Post  Graduate  Medical  School,  who  has  given  his 
valuable  counsel  and  encouragement  throughout  the  entire 
preparation  of  the  work ;  to  Dr.  W.  E.  Gordon,  Principal 
of  the  Patchogue  High  School,  for  his  suggestions  in 
adapting  the  work  to  the  practical  needs  of  the  pupils ; 
and  to  Dr.  Thomas  E.  Satterthwaite,  ex-vice  president  of 
the  New  York  Post  Graduate  Medical  School,  and  Dr. 
William  Pepper,  M.D.,  LL.D.,  ex-provost  of  the  Univer- 
sity of  Pennsylvania,  for  their  kind  criticisms  of  the  proof 
sheets.  Thanks  are  also  due  Professor  J.  O.  Lansing 
for  valuable  pedagogical  suggestions,  and  to  Mr.  Robert 
Cruger  for  suggestions  and  aid  in  the  illustrations. 

Patchogue,  N.Y. 


CONTENTS 


I.  Living  Bodies  and  Cells 

II.  Elements  of  the  Body     . 

III.  Oxidation 

IV.  Fermentation  and  Alcohol     . 
V.  Digestion  of  Food  in  the  Mouth 

VI.  Stomach  Digestion    . 

VII.  Abnormal  Action  of  the  Stomach 

VIII.  Intestinal  Digestion 

IX.  Absorption  and  Assimilation  . 

X.  Alcohol  and  Digestion    . 

XI.  Digestion  in  Lower  Animals   . 

XII.  Animal  Food       .... 

XIII.  Vegetable  Food 

XIV.  Quantity  of  Food  required     . 
XV.  Drinking  Water 

XVI.  Narcotics    .         .         . 

XVII.  Drugs  and  Poisons    ... 

XVIII.  The  Blood  .... 

XIX.  The  Heart  .... 

XX.  The  Flow  of  Blood  in  the  Body 

XXI.  Regulation  of  the  Flow  of  Blood 

7 


PAGE 

9 

22 

33 

41 

51 
66 

74 

79 
89 

98 

104. 

107 

120 

131 

135 

140 

148 
156 
162 
172 
185 


s 


CONTENTS 


CHAPTER 

PAGE 

XXII. 

The  Lungs       

192 

XXIII. 

Respiration  of  the  Tissues         .        .        .        . 

206 

XXIV. 

The  Air  and  Ventilation 

220 

XXV. 

Heat  and  Clothing       ..*... 

233 

XXVI. 

Excretion  and  Sewage         .... 

248 

XXVII. 

The  Skin  and  Bathing          .... 

256 

XXVIII. 

Nerves 

266 

XXIX. 

The  Spinal  Cord 

276 

XXX. 

The  Sympathetic  Nervous  System    . 

284 

XXXI. 

The  Brain 

289 

XXXII. 

Influences  which  affect  the  Mind  . 

305 

XXXIII. 

Effects  of  Narcotics  upon  the  Mind 

315 

XXXIV. 

Taste,  Smell,  and  Hearing 

323 

XXXV. 

The  Eye  

333 

XXXVI. 

The  Voice 

349 

XXXVII. 

Bones        

•    357 

XXXVIII. 

Joints 

•    364 

XXXIX. 

Muscles 

•    371 

XL. 

Bacteria  and  Disease 

.     382 

XLI. 

Repair  of  Injuries 

■    393 

glo.ssary 
Index     . 



.    401 

.    425 

APPLIED    PHYSIOLOGY 


-»oJ»ic 


CHAPTER    I 
LIVING  BODIES   AND   CELLS 

1.  What  physiology  is. — The  world  is  composed  of 
living  bodies  and  lifeless  matter.  In  livi7ig  bodies  there 
is  a  constant  change,  in  which  particles  become  lifeless 
and  are  thrown  off,  while,  at  the  same  time,  a  process  of 
creation  is  going  on  by  which  lifeless  matter  is  given  life. 
This  constant  destruction  and  renewal  of  the  particles  of 
the  body  constitutes  life. 

The  science  which  tells  of  the  structure  of  living  bodies 
is  Anato77iy ;  that  which  tells  of  their  working  is  Physi- 
ology;  and  that  which  tells  how  to  keep  living  bodies  in 
good  working  order  is  Hygiene.  The  term  physiology 
often  includes  anatomy  and  hygiene. 

Some  processes  in  man's  physiology  were  discovered 
only  by  studying  the  lower  animals ;  and  others,  by 
observing  plants.  In  fact,  it  is  by  studying  the  work- 
ings of  lower  forms  of  life  that  most  of  our  knowledge 
of  the  working  of  man's  life  has  been  gained.  The 
physiology  of  vegetables  and  animals  teaches  the  physi- 
ology of  man,  because  man  embodies  the  characteristics 
of  lower  forms  of  life.     During  the  course  of  ages  life  de- 

9 


10  APPLIED    PHYSIOLOGY 

veloped  through  vegetables  and   lower  animals  up  to  its 
highest  point  in  the  most  perfect  animal,  —  man. 

2.  The  ameba.  —  One  of  the  simplest  animals  lives  in 
stagnant  water  and  is  called  the  ameba.  It  is  only  a  lump 
of  jelly  about  yto  o^  ^^  ^^  ^^^^  ^^  diameter,  yet  it  is  a  com- 
plete animal,  for  it  moves,  and  eats,  and  grows,  and  pro- 
duces other  amebas.  It  has  no  arms,  or  legs,  or  head,  but 
all  parts  of  its  body  seem  very  nearly  alike.  It  puts  out 
little  fingers  from  its  body  and  then  rolls  its  whole  body 
into  the  fingers.  In  this  way  it  is  continually  rolling  about. 
When  it  finds  a  particle  of  food  it  wraps  itself  around  it 
just  as   a  baker   rolls  a  mass  of  bread  dough  around  a 


An  ameba,  sketched  at  intervals  of  ten  seconds  ( x  400) . 

raisin.  That  part  of  the  body  which  is  in  contact  with 
the  food  digests  as  much  as  is  needed,  and  then  unwraps 
itself  away  from  the  waste.  It  has  no  choice  as  to  what 
part  of  its  body  it  shall  use  for  any  given  purpose.  But 
man  uses  each  part  of  his  body  for  only  definite  purposes. 
He  has  arms  which  get  food,  a  mouth  which  eats  it,  and  a 
stomach  which  digests  it.  The  arms  cannot  eat  food, 
neither  can  the  mouth  digest  it,  but  each  part  does  only 
its  own  kind  of  work. 

3.  Man  like  an  ameba.  —  Each  part  of  a  man's  body  is 
made  of  multitudes  of  living  beings,  each  of  which  eats 
and  grows  like  an  ameba.  Each  tiny  being  is  called  a 
cell.  One  collection  of  cells  forms  the  skin,  another  the 
muscles  of  the  arm,  and  another  the  stomachy  and  so  oa 


LIVING   BODIES  AND   CELLS 


II 


Plants  and  animals  found 


through  the  body.  Each  collection  does  its  own  work, 
without  interfering  with  the  others.  The  cells  work 
together  like  a  well-trained  army,  so 
that  we  do  not  feel  the  workings  of 
each  separate  cell.  If  a  collection  is 
out  of  order,  the  person  is  sick. 

4.  Cells.  — -  Cells  are  of  various 
shapes,  according  to  the  work  they 
have  to  do.     They  are  from  5-0V0  ^^ 

y^  of   an  inch  in   length.       Each  cell  i^i  stagnant  water,  each  con- 
.     TT       .1  .   1     .    11  1    •        1  .        1         sistingofasinglecell(X20o). 

IS  like  thick  jelly  and  is  almost  color- 
less.    Near  its  center  a  small  mass  of   slightly  different 
composition  may  usually  be  distinguished.     This  central 

mass  is  called  the  nucleus. 
The  substance  composing 
the  cell  is  like  the  white  of 
an  ^g^  and  is  called  proto- 
plasm. Although  proto- 
plasm is 
transpar- 
ent and 
jellylike, 
yet  under 
a  micro- 
scope 
there  ap- 
pears an  interlacing  series  of  beads  and 
lines  which  suggest  a  structure  as  com- 
plex as  that  of  the  body  itself. 

5.  Connective  tissue. — The  cells  are 
tept  in  place  by  a  fine  network  of  strong  fibers  called  con- 
nective tissue.  In  some  parts  of  the  body,  as  on  the  outside 
of  the  muscles,  it  is  thick  and  skinlike,  but  around  each 


Cells  from  the  human  body  ( x  200) . 

a  A  colored  cell  from  the  eye. 

b  A  white  blood  cell. 

c  A  connective  tissue  cell. 

d  A  cell  from  the  lining  of  the  mouth. 

e  Liver  cells. 

/  A  muscle  cell  from  the  intestine. 


Diagram  of  the  parts 
of  a  cell. 

a   Nucleus. 

d  Cell-body  or  proto- 
plasm. 

c  Covering,  generally 
absent  in  animal 
cells. 


12  APPLIED    PHYSIOLOGY 

separate  cell  there  are  only  enough  fibers  to  keep  the  cell 
in  place.  Even  these  connective  tissue  fibers  are  the 
threadlike  arms  of  very  small  cells  set  apart  for  the 
menial  work  of  supporting  other  cells. 

6.  Three  tests  of  life.  —  We  know  that  each  cell  is  alive  ; 
for  it  moves,  it  takes  in  food,  and  it  multiplies. 

(i)  Motion.  —  Although  each  cell  is  held  in  place  by  the 
connective  tissue,  the  tiny  particles  of  its  body  are  in  con- 
stant motion,  just  as  a  boy's  eyes  and  mouth  and  hands 
and  feet  may  move,  even  if  he  sits  still  in  a  chair.  Besides 
this  continual  motion  of  the  particles  within  the  cell,  some 
cells  show  a  greater  motion,  in  which  the  cell  as  a  whole 
takes  part.  Thus,  a  muscle  cell  becomes  thicker  and 
shorter  when  the  muscle  bends  a  joint.  A  white  blood 
cell  can  force  its  way  through  the  wall  of  the  blood  tube,, 
and  can  wander  about  among  the  cells  of  the  body. 

(2)  Nutrition  and  Grozvth.  — The  blood  bathes  the  cells 
with  food  which  does  not  resemble  their  protoplasm.  Each 
cell  takes  in  the  food  through  any  portion  of  its  body,  and, 
endowing  it  with  life,  makes  it  a  part  of  itself.  Thus  each 
cell  increases  in  size. 

(3)  Reproduction.  —  During  the  period  of  growth  of  the 
body,  there  is  a  constant  production  of  the  cells ;  for  the 
man  is  composed  of  more  cells  than  the  child.  Even  in  a 
full-grown  man  certain  cells,  as  those  of  the  skin,  are  con- 
stantly being  shed  and  new  ones  formed.  When  a  cell 
reaches  mature  life,  the  nucleus  first  divides  into  two  parts, 
which  separate  from  each  other ;  then  the  body  of  the  cell 
divides  between  the  two  nuclei.  Thus  each  cell  becomes 
two  cells,  and  each  of  the  two  exactly  resembles  the  origi- 
nal cell,  except  that  it  is  smaller  at  first ;  but  it  soon  grows 
to  be  as  large  as  the  original  cell.  All  the  peculiarities  of 
the  life  of  the  first  cell  go  on  in  each  of  the  two  cells  inta 


LIVING  BODIES   AND   CELLS  1 3 

which  it  divides ;  and  so  we  say  that  the  new  cell  inherits 
the  peculiarities  of  the  parent.  This  process  may  be 
carried  on  very  rapidly ;  and  a  new  cell  may  be  produced, 
and  itself  become  divided,  in  a  few  hours. 

Anything  that  moves,  and  eats,  and  reproduces  itself  by 
means  of  its  own  power,  is  alive ;  and  so  the  cells  of  the 
body  are  alive  in  the  fullest  sense  of  the  term. 


Diagram  of  the  division  oi  a  cell. 

7.  Other  distinctions  between  the  living  and  the  dead.  — 

Many  living  bodies  will  show  some  spontaneous  niovemejit  in  response 
to  a  prick  or  a  blow,  or  other  irritation.  Certain  causes,  as  a  low  tem- 
perature, may  suspend  the  ability  to  respond  to  an  irritation,  but  it  will 
return  when  warmth  is  applied.  A  lifeless  thing  never  puts  forth  effort, 
no  matter  how  much  it  is  irritated. 

Decay  never  occurs  in  cells  while  they  live ;  but  after  death  disinte- 
gration soon  begins,  even  if  no  outside  power  acts  upon  the  cells.  On 
the  other  hand,  a  body  which  has  never  been  alive  usually  changes  very 
slowly  or  not  at  all,  unless  acted  upon  by  an  outside  power. 

8.  Relation  of  cells.  —  In  the  body  formed  by  the  cells 
there  exists  a  controlling  spirit  of  life,  whose  nature  is 
unknown.  When  all  the  cells  are  obedient  to  its  influence 
the  body  as  a  whole  is  alive  ;  but  if  the  cells  are  not 
obedient,  the  body  as  a  whole  is  dead,  although  each 
separate  cell  may  remain  alive.  For  example,  a  blow 
upon  the  head  may  disturb  this  controlling  influence  so 
that  it  cannot  tell  the  cells  how  to  act.  Then  they  instantly 
stop  work,  and  the  body  drops  dead.  Yet  each  cell  may 
remain  alive  for  minutes  or  hours,  just  as  each  soldier  may 
remain  alive  after  an  army  has  been  disbanded. 


14  APPLIED   PHYSIOLOGY 

9.  Tissues.  —  While  each  cell  eats,  grows,  and  pro- 
duces other  cells  more  or  less  independently  of  the  rest, 
yet,  Hke  the  members  of  a  large  family,  each  works  for 
the  benefit  of  all  the  others,  and,  in  turn,  is  dependent 
upon  them  for  things  which  it  cannot  do  so  well  as  they. 
Cells  doing  special  kinds  of  work  are  collected  in  orderly 
groups  called  tissues.  Six  kinds  of  tissues  are  well 
marked,  — 

(i)  Muscular  Tissue. —  Groups  of  ribbonlike  cells  which 
have  the  power  of  moving  the  adjacent  parts  are  found 
everywhere  in  the  body,  and  form  7nusculai'  tissue.  This 
tissue  is  usually  as  abundant  as  all  the  rest  of  the  tissues 
taken  together. 

(2)  Epithelial  Tissue.  —  Covering  all  the  surface  of  the 
body,  and  lining  every  cavity  and  tube  which  connects 
with  the  surface  of  the  body,  is  a  layer  of  firm  cells  which 
form  epithelial  tissue.  It  protects  the  underlying  parts 
and  manufactures  all  the  various  fluids  of  the  body. 
From  it,  also,  the  hair  and  nails  are  produced.  Epithelial 
tissue  is  abundant  and  important. 

(3)  Nervous  Tissue. — There  are  cells  which  control  all 
the  others.  By  means  of  their  long,  threadlike  prolonga- 
tions they  convey  orders  to  every  cell  in  the  body.  They 
and  their  prolongations  form  nervous  tissue. 

(4)  Connective  Tissue.  —  Surrounding  each  cell,  and 
holding  it  in  place,  are  the  extremely  fine  arms  of  small 
cells  called  cojinective  tissue  {^^^  p.  11).  Its  amount  varies 
greatly  in  different  parts  of  the  body  and  in  different  per- 
sons, but  its  total  amount  is  always  very  large.  In  some 
parts  of  the  body,  as  in  the  skin  and  lungs,  there  is  a 
special  kind  of  connective  tissue  which  is  very  elastic,  and 
gives  to  the  parts  their  stretching  properties.  This  tissue 
is  called  ''yellow  clastic  tissue^''  from  its  color. 


LIVING   BODIES   AND   CELLS  1 5 

(5)  Osseous  Tissue.  —  A  special  form  of  connective 
tissue,  in  which  enough  lime  is  mixed  to  make  it  stiff,  is 
called  bony  or  osseous  tissue.  This  tissue  is  rigid  and 
strong  so  as  to  form  a  framezvork  for  the  rest  of  the  cells 
of  the  body.  A  somewhat  similar  tissue,  containing  little 
or  no  lime,  is  called  cartilaginous  tissue.  It  surrounds  the 
jointed  ends  of  bones  and  often  becomes  bone  late  in  life. 

(6)  Adipose  Tissue.  —  Some  connective  tissue  cells  are 
arranged  in  microscopic  pockets  filled  with  oil  or  fat. 
This  forms  fatty  or  adipose  tissue.  Most  of  the  fat  in 
the  body  is  stored  in  this  way  (see  p.  25). 

10.  The  blood  as  a  tissue.  —  Blood  contains  two  kinds  of 
cells,  each  of  which  has  a  special  work  to  do.  The  fluid 
in  which  the  cells  float  can  become  solid,  and  therefore 
blood  is  really  a  tissue.  The  lymph,  w^hich  is  mainly 
diluted  blood,  may  also  be  considered  a  tissue. 

11.  Other  fluids  in  the  body.  —  There  are  other  fluids  in 
the  body  which,  while  they  contain  a  few  cells,  do  not 
depend  upon  them  for  their  properties  or  actions  and  so 
are  not  tissues.  Into  the  digestive  tube  there  are  poured 
Ave  fluids  concerned  in  digestion,  viz.  :  the  saliva,  the 
gastric  juice,  the  pancreatic  juice,  the  bile,  and  the  intes- 
tinal juice.  In  order  to  carry  off  the  waste  products  of 
the  body  two  fluids,  the  pej'spiratioji  and  the  urine,  are 
continually  being  formed,  while  water  is  given  off  in 
gaseous  form  by  the  breath.  Three  fluids  are  found  in 
connection  with  the  eye.  Two,  called  the  aqueous  and 
the  vitreous  humors,  distend  the  eyeball,  and  another, 
called  tears,  runs  over  its  surface  to  wash  away  dirt.  In- 
side the  cavity  of  each  joint  is  a  thick  fluid,  called  synovia, 
which  lubricates  the  surface  of  the  bones  within  the  mov- 
able joints.  Lastly,  milk  is  sometimes  produced  for  the 
nourishment  of  the  young. 


l6  APPLIED    PHYSIOLOGY 

12.  Organs.  —  In  order  to  work  to  the  best  advantage, 
several  kinds  of  tissues  are  usually  associated  together. 
Thus,  the  stomach,  which  digests  food,  is  composed  of 
muscular  tissue  which  moves  the  food  about,  and  epithelial 
tissue  which  pours  out  digestive  fluids,  and  nervous  tissue 
which  presides  over  the  process,  while  connective  tissue 
binds  the  whole  together.  A  collection  of  different  tis- 
sues always  arranged  in  a  definite,  compact  shape  for  a 
special  purpose,  is  called  an  organ.  The  stomach,  intestine, 
pancreas,  and  the  liver  are  the  four  principal  organs  of 
digestion.  The  Inngs  are  orgajts  of  respiration,  the  heart 
is  an  organ  for  the  propulsion  of  blood.  The  kidneys  and 
skin  are  organs  which  get  rid  of  waste  matter,  and  the 
brain  is  the  07gan  of  thought.  The  term  organ  is  also 
applied  to  many  other  parts  of  the  body,  but  these  are 
the  principal  ones. 

13.  Systems.  —  Sometimes  a  definite  series  of  tissues 
and  organs  are  not  arranged  in  compact  form,  but  are 
scattered  through  the  whole  body.  This  forms  a  system. 
Thus  the  system  of  tubes  formed  of  muscular  and  con- 
nective tissue  in  which  the  blood  moves  is  called  the 
circulatory  system,  while  the  heart  is  an  organ  in  the  cir- 
culatory system.  In  the  same  way  the  brain  is  an  organ 
in  the  nervous  system.  The  five  main  systems  are  the 
digestive,  circulatory,  respiratory,  nervous,  and  excretory 
systems.  In  Physiology  the  action  of  the  cells  of  each 
tissue,  organ,  and  system  is  studied  separately.  The 
structure  and  arrangement  of  the  cells  of  each  tissue 
arc  studied  by  means  of  a  microscope. 

14.  The  microscope.  —  In  order  to  show  even  the  largest 
cell,  a  compound  microscope  magnifying  at  least  twenty 
times  is  needed ;  while  for  ordinary  use,  one  magnifying 
at  least  two  hundred  times  is  necessary. 


LIVING    BODIES   AND    CELLS 


17 


A  compound  microscope  consists  of  two  lenses  set  in  a 
movable  tube.  The  lower  lens  is  called  the  objective^  and 
does  the  main  part  of  the  magnifying.  It  can  easily  be 
removed  from  the  tube  or  swung  aside,  and  another 
objective  of  different  magnifying  power  substituted  for  it. 


COARSE    AOJUS 


FINE 


Rca 

FOR  LIGHTiSG 
SPECIMEN 


Compound  microscope. 


The  upper  lens  is  called  the  eyepiece.  It  can  be  re- 
moved from  the  tube,  and  another  substituted.  Usually 
two  or  three  objectives  and  two  eyepieces  of  different 
magnifying  powers  are  furnished  with  each  microscope. 
A  microscope  is  said  to  magnify  as  many  diameters  as 
the  number  of  times  it  enlarges  the  breadth  or  diameter 

OV.  PHY5I0L.  —  2 


l8  APPLIED    PHYSIOLOGY 

of  an  object.  Thus  a  microscope  making  a  cell  appear 
100  times  as  broad  as  it  really  is,  is  said  to  magnify  lOO 
diameters.  But  the  length  and  thickness  are  also  magni- 
fied. So  the  surface  of  the  cell  is  made  lOO  x  lOO  or 
10,000  times  as  large,  while  its  bulk  is  100  x  100  x  100 
or  1,000,000  times  as  large.  A  table  accompanying  each 
instrument  tells  the  power  of  each  combination  of  lenses. 

15.  Arrangement  of  the  light.  —  A  small  mirror  placed  at  the 
lower  part  of  the  microscope  throws  light  through  the  object,  for  other- 
wise there  would  not  be  sufficient  light  to  spread  over  its  magnified 
surface.  The  mirror  can  be  tilted  so  as  to  catch  the  light  from  any 
direction.  Objects  usually  show  best  when  they  are  lighted  only  suf- 
ficiently to  show  their  outlines.  A  stronger  light  may  pass  through 
extremely  small  objects  so  that  they  do  not  show  at  all.  Each  micro- 
scope usually  has  a  device  for  varying  the  size  of  the  aperture  in  the 
plate  upon  which  the  specimen  rests,  thus  again  regulating  the  amount 
of  light.  It  is  usually  not  best  to  use  an  amount  of  light  which  makes 
the  field  of  view  brilliant. 

16.  Focusing.  — The  tube  carrying  the  lenses  can  be  moved  up 
and  down  by  means  of  a  small  wheel.  Arranging  the  distance  of  the 
lens  from  the  specimen  is  called  fociisijig.  An  objective  of  high  mag- 
nifying power  must  be  much  nearer  to  the  specimen  than  one  of  low 
power.  Thus  an  objective  magnifying  500  diameters  must  be  about 
^5  of  an  inch  from  the  "specimen,  while  one  magnifying  50  diameters 
would  be  over  half  an  inch  distant.  For  high  magnifying  powers 
the  focusing  must  be  very  exact.  So  a  second  wheel  is  provided 
which  moves  the  tube  very  slowly.  This  wheel  is  called  the  fine  ad- 
justment in  distinction  from  the  other  wheel  or  coarse  adjustment. 
The  finger  of  the  observer  should  always  be  upon  the  fine  adjustment, 
turning  it  back  and  forth  so  as  to  observe  now  the  top  and  now  the 
deeper  portions  of  the  specimen,  for  it  is  magnified  in  depth  as  well  as 
in  breadth. 

It  is  often  very  difficult  to  find  a  very  small  specimen  with  a  high 
power  lens,  for  the  space  in  which  it  lies  is  magnified  to  several  feet  in 
diameter.  A  good  plan  is  to  use  a  low  power  lens  for  finding  the  speci- 
men, and  then  after  bringing  it  to  the  center  of  the  field,  to  substitute 
the  high  power  lens. 


LIVING   BODIES   AND    CELLS  1 9 

Every  movement  of  the  specimen  is  magnified  as  much  as  the  speci- 
men itself.  So  great  gentleness  is  needed  in  moving  it  under  the  ob- 
jective or  else  it  will  be  moved  out  of  view  altogether.  The  microscope 
appears  to  reverse  the  sides  of  the  specimen,  so  in  order  to  move  the 
image  in  anv  direction  the  specimen  must  be  moved  in  the  opposite 
direction.  Care  should  be  taken  not  to  press  the  lens  upon  the  speci- 
men. If  the  lens  becomes  dirty  or  moist  it  should  be  gently  wiped 
with  a  soft,  clean  handkerchief.  A  little  alcohol  rubbed  on  will  aid  in 
removing  the  dirt. 

17.  Preparation  of  specimens.  —  Specimens  are  examined 
upon  glass  plates,  called  slides.  The  regulation  size  is 
three  inches  long  and  one  inch  broad.  Specimens  must 
be  very  thin,  so  as  to  show  only  a  single  layer  of  cells  or 
fibers.  A  liquid  specimen  should  be  a  small  drop ;  a  powder 
should  be  only  a  tiny  speck.  A  solid  specimen  is  prepared 
in  either  of  two  ways.  Its  cells  and  fibers  may  be  picked 
apart  by  means  of  two  needles  ;  but  this  destroys  the 
natural  arrangement  of  the  parts.  So  the  method  of 
slicing  off  extremely  thin  layers  with  a  sharp  razor  is 
more  often  used.  This  requires  special  training.  Nearly 
all  specimens  should  be  examined  in  a  liquid.  Water  will 
do  for  nearly  all.  Glycerine  may  be  used  if  the  specimen 
is  to  be  kept,  for  it  does  not  evaporate.  A  drop  is  placed 
over  the  specimen  on  the  slide.  Over  the  drop  of  liquid 
it  is  well  to  place  a  thin  piece  of  glass,  called  a  cover  glass, 
for  the  purpose  of  protecting  the  objective  from  the 
liquid,  and  the  specimen  from  currents  of  air.  Air  bub- 
bles under  the  cover  glass  interfere  with  the  view.  They 
can  be  forced  out  by  gently  pressing  upon  the  cover  glass ; 
but  with  care  the  cover  glass  can  be  applied  so  as  to  avoid 
them.  A  supply  of  slides  and  cover  glasses  is  a  necessary 
part  of  every  microscopic  outfit. 

A  few  fibers  scraped  off  from  a  handkerchief  or  a  few 
scales  from  the  back  of  the  hand  are  good  specimens  for 


20  APPLIED    PHYSIOLOGY 

practice.  A  tiny  bit  should  be  placed  upon  a  slide  and  a 
drop  of  water  placed  upon  it,  and  the  whole  covered  with 
a  cover  glass.  Begin  to  examine  it  with  the  lowest  powers 
of  the  microscope,  and  so  gradually  learn  to  use  the  higher 
powers. 

SUMMARY 

1 .  Physiology  tells  how  living  beings  eat  and  grow  and  act. 

2.  The  ameba  is  a  tiny  lump  of  living  jelly,  which  eats, 

and  moves,  and  produces  young  amebas. 

3.  The  body  of  a  man  is  made  of  tiny  cells  like  an  army 

of  amebas. 

4.  Each  cell  is  a  lump  of  thick  jelly,  in  which  a  small 

mass  called  the  nucleus  may  usually  be  distin- 
guished. The  cells  are  held  in  place  by  strings 
called  comiective  tissue. 

5.  Each  cell  moves,  eats,  and  grows,  and  produces  other 

cells  like  the  first. 

6.  The  mind  lives  in  the  body  formed  by  the  cells. 

7.  The  cells  obey  the  mind.     When  the  mind  loses  con- 

trol of  them  the  body  is  dead. 
S.    Each   cell  does   some   special    kind   of  work  for   the 

benefit  of  the  rest. 
9.    A  collection  of  cells  doing  a  special  kind  of  work  is 

called  a  tissue. 

10.  A  collection  of  different  tissues  always  arranged  in  a 

definite  and  compact  shape  is  called  an  organ. 

11.  A    definite    series    of    tissues   and    organs    scattered 

through    the    body  for  a  definite  purpose  forms  a 
system. 

DEMONSTRATIONS 

I.    Scrape  the  inside  of  the  cheek  with  a  sharp  knife  and  examine 
a  drop  under  the  microscope,  with  a  power  of  at  least  100  diameters. 


LIVING   BODIES  AND    CELLS  21 

Notice  the  flat  scales  of  irregular  shape.  Each  scale  is  a  separate 
living  cell.  It  is  nearly  transparent,  but  its  nucleus  appears  as  a 
slightly  darker  spot.     Make  a  drawing  of  the  cells. 

Examine  cells  scraped  from  the  skin  upon  the  back  of  the  hand ; 
and  cells  scraped  from  the  pulp  of  a  leaf.  Examine  a  bit  of  the  green 
scum,  called  pond  aigcE,  which  forms  upon  stones  in  fresh-water  ponds. 
Notice  the  long  cells  joined  end  to  end  and  containing  green  matter. 

2.  Take  a  drop  of  stagnant  slimy  water  from  a  rain  barrel  or  from  a 
kitchen  drain  or  from  a  stagnant  pool.  Examine  it  with  a  power  of  at 
least  I  GO  diameters.  A  specimen  of  the  ameba  is  likely  to  be  found 
rolling  about.  Notice  its  nucleus,  and  also  dark  spots  in  its  body  which 
are  probably  food  which  it  has  swallowed.    Make  a  sketch  of  an  ameba. 

REVIEW  TOPICS 

1.  Define  Anatomy. 

2.  Define  Physiology. 

3.  Define  Hygiene. 

4.  Describe  an  ameba. 

5.  Describe  a  cell. 

6.  Describe  conjiective  tissue. 

7.  Give  the  three  tests  by  which  a  cell  or  other  body  is 

known  to  be  alive. 

8.  Give    other  distinctions   between   living  and   lifeless 

bodies. 

9.  Give  the  relation  of  the  mind  to  the  cells  of  the  body. 

10.  Define  a  tissue  and  name  the  different  tissues  of  the 

body. 

11.  Show  that  the  blood  is  a  tissue. 

12.  Give  the  different 7?// z'<afi-  in  the  body. 

13.  Define  an  organ. 

14.  Define  a  system. 

15.  Describe  the  instrnment  by  means  of  which  the  dif- 

ferent cells  and  tissues  of  the  body  are  studied. 


CHAPTER    II 
ELEMENTS   OF   THE  BODY 

18.  Proximate  principles.  —  The  cells  of  all  animals  con- 
tain the  same  substances,  differing  in  amount  and  arrange- 
ment, yet  alike  in  composition.  The  simple  substances  of 
which  the  cells  are  composed  are  zd^o,^  proximate  principles. 
The  most  important  proximate  principles  are  water,  albu- 
min, fat,  sugar,  salt,  lime,  soda,  and  potash. 

19.  Water  and  solution.  —  Water  forms  nearly  three 
fourths  of  the  weight  of  the  body  and  is  present  in  every 
part.  It  reaches  each  minute  part  of  the  body  through 
the  firm  walls  of  the  organs.  Water  has  the  power  of 
dissolving  solid  substances,  so  that  they  retain  all  their 
properties  unchanged.  Sugar  in  water  is  sugar  still ;  in 
fact,  we  can  appreciate  what  sugar  is  only  when  it  is  dis- 
solved. When  a  substance  is  dissolved  in  a  liquid,  so  that 
each  remains  unchanged  in  its  essential  properties,  the 
result  is  a  solution.  Most  solutions  will  go  anywhere 
water  itself  will  go.  In  the  stomach  the  food  becomes 
dissolved,  and  is  taken  into  the  blood  tubes.  The  blood 
contains  a  solution  of  food  which  penetrates  into  the  spaces 
around  each  cell,  carrying  nourishment  to  the  cell  and 
washing  away  its  waste  matters.  Water  makes  the  tissues 
limber  and  slippery,  so  that  they  bend  and  move  easily. 
By  means  of  the  perspiration  which  carries  off  surplus  heat, 
water  regulates  the  heat  of  the  body.  About  three  quarts 
of  water  are  taken  into  the  body  each  day. 

22 


ELEMENTS    OF   THE   BODY  2$ 

Water  is  composed  of  two  gases,  hydrogen  and  oxygen^ 
very  firmly  united. 

20.  Albumin.  —  The  protoplasm  of  the  living  cells  of  the 
body  is  almost  entirely  composed  of  a  substance  like  the 
white  of  an  Qgg.  Because  it  turns  white  when  heated,  it 
is  called  albumin  (from  the  Latin  albus,  white).  Pure 
albumin  is  hard  and  brittle  as  the  white  of  an  ^gg  is  when 
it  is  dry.  In  the  body  it  is  dissolved  in  from  five  to  twenty 
times  its  own  weight  of  water.  This  solution  in  water  is 
what  is  meant  by  the  albumin  of  the  body.  In  the  blood 
it  is  liquid,  in  the  flesh  it  is  somewhat  jellylike,  and  in 
the  skin  it  is  strong  and  tough.  It  is  a  very  complex 
body  which  only  plants  can  form.  Animals  must  get  it 
from  vegetables  and  change  it  into  their  OAvn  bodies. 
When  once  formed  it  may  become  part  of  the  bodies- 
of  several  successive  animals,  as  one  makes  food  of 
another. 

Albumin  forms  the  principal  part  of  the  protoplasm  of 
all  living  cells.  Some  is  used  in  performing  the  work  of 
the  body  and  does  not  reach  the  cells.  About  four  and 
one  half  ounces  of  pure  albumin  must  be  eaten  each  day 
to  supply  the  needs  of  the  body. 

21.  Forms  of  albumin.  —  There  are  many  forms  of  albumin,  all 
having  essentially  the  same  properties.  Tne  white  of  eggs  is  almost 
pure  albumin.  Lean  meat  is  composed  mostly  of  another  form  ;  cheese^ 
gelatine,  and  glue  are  composed  mainly  of  still  other  forms. 

22.  Coagulation.  —  Most  forms  of  albumin  may  be  hard- 
ened either  by  heat  or  acids,  and  once  hardened  they  can- 
not be  dissolved  again  to  their  original  state.  A  boiled 
^gg  illustrates  this  hardening.  Changing  a  hquid  to  a 
jellylike  or  sohd  form  so  that  it  cannot  be  changed  back 
to  its  original  form  is  coagulation.  Coagulation  of  its 
albumin  destroys  the  life  of  a  cell. 


24 


APPLIED  PHYSIOLOGY 


23.  Putrefaction.  — When  albumin  is  kept  moist  and  exposed  to 
the  warm  air  it  decays  or  putrefies,  becoming  soft  and  finally  completely 
dissolving,  and  at  the  same  time  giving  off  offensive  odors.  If  the 
albumin  is  kept  dry  it  shrivels  up  and  finally  crumbles  to  an  odorless 
powder.  Pure  sugar  or  fat  will  not  putrefy,  although  both  may  become 
sour,  but  both  often  contain  a  slight  amount  of  albumin,  and  this  may 
putrefy,  giving  them  a  slight  taste  and  odor. 

24.  Diffusion.  —  When  salt  and  water  are  placed  in  a 
"bag  of  thin  skin  and  suspended  in  a  dish  of  water,  some 

of  the  salt  and  water  will  pass  through 
the  walls  of  the  bag  and  will  mingle 
with  the  water  in  the  dish,  and,  on  the 
other  hand,  some  water  will  pass  into 
the  bag.  This  will  go  on  until  the 
water  in  the  dish  is  of  the  same  salt- 
ness  as  the  water  in  the  bag.  The  act 
of  passing  through  a  membrane  appar- 
ently impervious  is  a  form  of  dijfiision. 
Without  pressure  albumin  will  not  dif- 
fuse except  in  the  form,  called /^//^z/^', 
which  is  produced  from  the  others  by 
digestion.  Peptone  readily  diffuses 
through  the  thin  sides  of  the  blood 
tubes  in  the  walls  of  the  intestine,  and 
so  reaches  the  blood. 


Diffusion  at  the  begin 
ning  of  the  process. 


Diffusion  at  the  end 
of  the  process. 


25.  Iron-bearing  albumin.  —  The  nu- 
cleus of  vegetable  cells  is  composed  of  a  form  of 
albumin  called  7iucleo-albu7nin,  which  contains 
iron.  There  are  from  thirty  to  sixty  grains  of 
iron  in  the  human  body,  all  of  which  is  united  with  the  albumin,  so 
that  the  metallic  properties  of  the  iron  are  completely  absent.  A 
small  amount  of  this  iron-bearing  albumin  is  found  in  the  nucleus  of 
every  cell,  both  vegetable  and  animal,  and  seems  to  be  essential  to  the 
growth  and  division  of  the  cell.  In  an  animal  this  substance  gives 
origin  to  the  substance  called  hemoglobin,  which   forms  the  coloring 


ELEMENTS   OF  THE  BODY  2$ 

matter  of  the  red  blood  cells.  The  iron  gives  it  the  power  to  carry 
oxygen  from  the  lungs  to  all  parts  of  the  body.  Only  one  or  two 
grains  of  iron  are  required  each  day  to  supply  the  loss  of  the  iron  in 
the  body,  and  several  times  that  amount  is  eaten  daily  in  our  food. 

26.  Fats  and  oils.  —  Fats  are  a  series  of  smooth,  slip- 
pery substances  found  in  all  animals,  and  in  most  vege- 
tables. About  five  per  cent  of  the  human  body  is  fat.  It 
is  scattered  between  the  cells  of  all  parts  of  the  body,  but 
in  places,  as  in  'the  walls  of  the  abdomen,  it  forms  thick 
layers.  All  fats  become 
liquid  when  heated,  but 
those  that  are  liquid  at 
ordinary  temperatures  are 
called  ou's.  In  the  living 
body  fat  is  always  in  a 
liqtnd  state,  stored  in 
thin-walled  pockets  made 
of  connective  tissue.  By 
boiling,  the    pockets   are  Fat  tissue  (x  loo). 

r,  J  J   4-U^  -f^*- r.   Connective  tissue  cells  form  pockets  in  which 

softened  and  the  fat  runs  ^^^  ^.^^.^  ^^^  .^  /^^^^_ 

out  upon  the  water.   Each 

pocket  is  from  ^^  to  ^-g-  of  an  inch  in  diameter.  The  fat 
is  produced  from  the  albumin  of  the  cells  by  a  breaking- 
down  process.  Fat  is  a  simple  substance  compared  with 
the  complex  albumin.  Probably  all  the  fat  which  is  stored 
in  the  body  is  made  out  of  albumin. 

27.  Emulsion  of  fat.  —  However  much  fat  may  be  shaken  wi*-h 
water  it  will  remain  in  tiny  particles  which  soon  rise  to  the  surface.  If 
a  little  white  of  egg  is  added,  the  fat  will  divide  into  finer  particles  and 
will  remain  in  the  water  much  longer.  A  mixture  of  fat  and  water  is  an 
ejnulsion.  No  emulsion  is  permanent,  but  the  fat  will  rise  to  the  surface 
in  time.  Milk  is  the  most  perfect  emulsion,  but  even  in  milk  the  cream, 
or  fat,  rises  in  a  few  hours. 


26 


APPLIED   PHYSIOLOGY 


28.  SaT)Onification  of  fats.  — When  fat  is  boiled  with  soda  or 
potash  it  is  broken  up  into  a  small  amount  of  glycerine  and  a  large 
amount  of  a  substance  called  a  fatty  acid.  The  fatty  acid  unites  with 
the  soda  or  potash  to  form  soap.  When  by  any  means  fat  is  broken, 
up  with  soda  or  potash,  forming  soap,  the  process  is  called  saponifica- 
tion.  Both  soaps  and  emulsions  are  continually  being  formed  during 
the  digestion  of  fat. 

29.  Use  of  fat.  —  The  fat  of  the  body  is  a  living  garment, 
retaining  heat  and  protecting  the  body  from  the  cold,  and 
rounding  out  the  rugged  outlines  of  the  bones  and  muscles. 
It  is  a  cushion,  protecting  the  internal  organs  from  injury. 
It  is  also  a  store  of  food  to  be  used  in  sickness  when  food 
cannot  be  eaten.  The  fat  which  is  eaten  is  used  up  in 
warming  the  body.  Thus  fat  acts  as  a  food,  as  armor  for 
the  body,  and  as  useful  and  ornamental  clotJiijig.  About 
three  ounces  of  fat  must  be  eaten  each  day. 

30.  Starch  and  sugar.  —  Starch  is  produced  almost  en- 
tirely by  plants  and  is  stored  in  the  form  of  little  grains 

which  will  not  dis- 
solve in  cold  water. 
Grains  of  potato  starch 
appear  like  oyster 
shells  and  show  dis- 
tinct markings  as 
though  they  were  built 
up  in  layers.  It  is 
supposed  that  starch 
grains  grow  by  deposits 
of  successive  layers  of  starch  between  which  are  layers  of 
a  waterproof  substance  called  cellulose  or  plant  connective 
tissue.  When  the  grains  are  boiled,  they  swell  and  burst 
and  then  dissolve,  forming  a  paste.  As  a  plant  grows,  it 
uses  the  starch  in  building  up  sugar,  wood,  cotton,  cellu- 
lose, and  other  plant  substances.     Starch,  sugar,  wood,  cot- 


starch  Grains  ( x  400) . 
a,  of  potato.         b,  of  corn. 


ELEMENTS   OF  THE   BODY 


2; 


A  thin  slice  of  potato  ( x  200) . 

a   Albuminous  and  fibrous  pockets. 
b    Starch  grains  in  the  pockets. 


ton,  and  cellulose  are  similar  in  chemical  composition,  but 
differ  widely  in  character. 

Wood  is  of  no  use  to 
the  body,  but  starch  and 
sugar  are  common  foods. 
Starch  is  changed  to 
sugar  before  it  becomes 
a  part  of  the  body  of 
man.  Only  a  little  sugar 
is  found  in  the  body  at 
one  time,  for  almost  as 
fast  as  it  enters  it  is 
used  up  to  produce 
warmth.  About  five 
ounces  of  starch  or  sugar 
must  be  eaten  each  day. 

Minerals.  —  The  minerals  salt,  lime,  soda,  and  potash, 
are  always  found  in  the  body. 

31.  Salt.  —  Common  salt  is  found  in  the  bodies  of  all 
animals,  and  a  less  amount  in  vegetables  also.  There  are 
about  six  or  seven  ounces  of  salt  in  the  human  body.  In 
animal  food  there  is  enough  salt  to  supply  the  needs  of 
the  body,  but  some  must  be  added  to  vegetable  food.  So 
flesh-eating  animals,  like  dogs  and  cats,  will  not  eat  salt, 
while  vegetable-feeding  animals,  as  horses,  like  it. 

Salt  gives  an  agreeable  taste  to  food,  and  this  causes  the  '"mouth  to 
water,"  and  all  the  other  digestive  fluids  to  flow  freely,  so  that  the  salted 
food  is  quickly  and  easily  digested. 

Some  kinds  of  albumin  in  the  body  will  dissolve  in  water  only  when 
salt  is  present,  and  if  it  is  diminished  in  amount,  or  is  absent,  these 
albumins  cannot  do  their  work. 

Salt  diffuses  very  readily,  and  also  aids  in  the  diffusion  of  all  kinds 
of  food.  So  salt  has  very  important  uses  in  the  body,  and  when  it  is  not 
used  there  is  great  suffering.     The  proper  amount  of  salt  is  present  in 


28  APPLIED   PHYSIOLOGY 

the  food  when  food  tastes  just  agreeably  salt.     About  one  half  an  ounce 
needs  to  be  eaten  each  day. 

32.  Lime.  —  A  small  amount  of  lime  is  found  every- 
where in  the  body,  but  bone  is  over  one  half  lime.  In  all, 
there  are  between  ten  and  twelve  pounds  of  lime  in  the 
body,  but  only  six  grains  need  be  eaten  each  day.  Much 
more  than  this  amount  is  found  in  all  common  food.  The 
main  use  of  lime  is  to  give  stiffness  to  the  bones.  It  is 
mixed  with  the  cells  and  fibers  of  the  bone,  just  as  starch 
is  mixed  with  the  fibers  of  linen  to  make  it  stiff. 

33.  The  alkalies  —  soda  and  potash.  —  Some  substances 
are  sour  and  burning  to  the  taste,  and  can  corrode  or  eat 
away  flesh  and  metals.  When  soda  or  potash  is  mixed 
with  such  a  substance,  both  ingredients  in  the  mixture  are 
changed  and  a  new  substance  unlike  either  is  formed. 
For  instance,  strong  vinegar  is  such  a  sour,  corrosive  sub- 
stance. When  soda  is  added  to  it  the  mixture  bubbles  for 
a  time,  and  then  the  liquid  is  no  longer  sour  or  irritating, 
but  has  a  fiat,  bitter  taste,  and  both  the  soda  and  vinegar 
have  become  changed.  A  substance  which  is  sour  to  the 
taste  and  corrodes  metals  and  flesh,  and  unites  with  soda 
or  potash  with  a  bubbling,  is  called  an  acid.  Soda  and 
potash  are  called  alkalies.  They  also  can  corrode  certain 
substances,  but  they  always  unite  with  acids  at  the  first 
opportunity,  and  by  their  union  each  is  changed  to  a 
less  harmful  form.  So  alkalies  destroy  or  neutralize 
actds,  and  acids  neutralize  alkalies. 

34.  Chemical  action.  —  When  two  substances  are  mixed 
together  so  that  each  becomes  changed  and  substances 
unlike  either  are  produced,  the  process  is  called  chemical 
action.  Sugar  will  dissolve  in  vinegar,  but  it  still  remains 
sugar,  and  so  the  mixture  is  called  a  solution  (see  p.  22). 
In  contrast  with  it,  when  soda  is  dissolved  in  vinegar  it  is 


ELEMENTS   OF  THE   BODY  29 

completely  changed,  and  so  forms  an  example  of  chemical 
action.  Some  substances  are  very  prone  to  mix  to  form 
solutions.  Thus,  impure  salt  has  such  an  attraction  for 
water"  that  it  takes  it  from  the  air  and  becomes  damp.  So 
salt  is  said  to  have  an  affinity  for  water.  In  the  same 
way  some  substances  are  very  prone  to  mix  so  as  to  be- 
come changed  by  chemical  action.  Thus,  there  is  always 
chemical  action  between  soda  and  vinegar  when  they  are 
brought  together,  so  soda  is  said  to  have  a  chemical 
affinity  for  vinegar.  In  the  same  way,  air  has  a  great 
*'  chemical  affinity  "  for  wood  in  a  fire.  The  chief  value  of 
gold  comes  from  the  fact  that  it  has  no  chemical  affinity  at 
all  except  for  one  or  two  uncommon  substances.  So  it 
will  remain  unaltered  in  the  midst  of  substances  which 
would  destroy  other  metals. 

35.  Use  of  alkalies.  —  If  a  fluid  contains  an  acid,  it  is 
said  to  be  acid  in  reaction  ;  if  an  alkali  it  is  alkali^ie ;  and  if 
it  contains  neither  it  is  neutral  in  reaction.  Now,  the  blood 
is  always  alkaline  from  the  presence  of  a  small  amount  of 
soda  and  potash.  Acid  products  are  being  formed  in  the 
body  continually,  and  the  duty  of  the  alkalies  is  to  unite 
with  them  at  once  and  change  them  to  harmless  sub- 
stances, which  may  be  handled  by  the  blood  in  safety. 
The  alkalies  are  found  in  nearly  all  foods. 

36.  Chemical  actions  in  the  body.  —  Everything  which  makes 
up  the  cells  and  fluids  of  the  body  is  composed  of  some  or  all  the  sub- 
stances—  water,  albumin,  fat,  sugar,  or  starch,  with  the  minerals  — 
salt,  lime,  and  soda  and  potash.  These  must  be  eaten  to  sustain  life, 
and  so  they  are  foods.  Other  kinds  of  substances  are  harmful  or 
poisonous.  All  food  substances  are  eaten  three  times  a  day,  and  yet 
only  water  and  the  minerals  leave  the  body  in  anything  like  the  form 
in  which  they  entered.  The  rest  are  entirely  changed  by  chemical 
actions  and  leave  the  body  as  gases  or  liquids  or  as  solids  dissolved  in 
water.     The  digestion  of  food  from  the  time  it  is  taken  into  the  mouth 


30  APPLIED   PHYSIOLOGY 

is  a  chemical  action,  as  is  also  its  becoming  a  part  of  the  living  cells. 
Breathing  and  the  production  of  the  waste  matters  of  the  body  are 
also  chemical  processes. 

These  chemical  processes  can  be  followed  and  even  imitated  in  a 
laboratory.  The  living  principle  in  the  body  directs  the  work,  but 
uses  few  processes  which  are  not  also  used  outside  of  the  body.  It  has 
been  a  great  triumph  for  science  to  liberate  men  from  the  superstition 
that  the  chemical  and  physical  laws  of  our  bodies  were  governed  by  the 
arbitrary  feelings  of  indwelling  spirits,  and  so  were  different  from  the 
laws  governing  lifeless  creatures. 

SUMMARY 

1.  The  cells  of  the  body  are  composed  of  five  substances, 

viz.,  water,  albumin,  fat,  sugar,  and  minerals. 

2.  Water  is  three  fourths  of  the  body.     It  carries  food  to 

the  cells  and  washes  away  their  waste  matters. 

3.  Albumin  is  like  the  white  of  eggs.     It  forms  the  pro- 

toplasm of  all  cells.     It  warms  the  body,  and  gives 
it  strength  and  weight 

4.  Fat  is  in  pockets  between  the  cells.     It  protects  and 

heats  the  body. 

5.  Starch  and  sugar  are  similar  substances.     They  warm 

the  body. 

6.  The   minerals   in    the   body   are    salt,  lime,  soda,  and 

potash.     They  are  found  in  all  food.     In  addition 
some  salt  must  be  eaten. 

7.  Salt  aids  in  the  preparation  and  distribution  of  food  to 

the  cells  of  the  body. 

8.  Lime  stiffens  the  bones. 

9.  Soda  and  potash  destroy  irritating   acids  within    the 

body. 

10.  Water,  albumin,  sugar  or  starch,  fat  and  minerals,  are 

foods  and  must  be  eaten  to  sustain  life. 

11.  Most  of  the  vital  actions  of  the  body  can  be  imitated 

in  a  chemical  laboratory. 


ELEMENTS    OF   THE   BODY  3 1 

DEMONSTRATIONS 

3.  Illustrate  the  properties  of  albumin  by  the  white  of  an  egg. 
Notice  its  sticky  character.  Dry  some  upon  a  piece  of  paper  over  a 
fire  and  notice  its  brittle,  gluelike  character,  and  that  it  will  again  dis- 
solve in  water.  Boil  some  and  notice  that  it  becomes  hard  and  will 
not  redissolve.     Set  some  aside  and  notice  that  it  decays. 

4.  Inclose  a  lump  of  wet  llour  in  a  muslin  bag  and  wash  it  until  the 
water  is  clear.  This  removes  the  starch  grains  and  leaves  the  grain 
albumin  or  glziten  pure.     Notice  its  tough  and  sticky  character. 

5.  Show  samples  of  olive  oil,  lard,  and  tallow.  Show  that  lard 
melts  at  about  the  temperature  of  the  body,  and  so  is  fluid  in  the  body. 

6.  Shake  together  some  oil  and  water.  Notice  that  the  oil  at  once 
floats  upon  the  surface.  Now  shake  the  oil  with  some  lime  water,  and 
notice  that  it  no  longer  floats,  but  that  the  mixture  looks  milky,  while  a 
few  very  small  oil  drops  can  be  seen  floating  in  the  liquid.  Explain 
that  this  is  an  eimdsion. 

7.  Stir  together  some  castor  oil  and  caustic  soda,  gently  heating  the 
mixture,  and  notice  that  it  forms  soap. 

8.  Scrape  a  potato  into  a  basin  of  water.  Wash  it  about  and  notice 
that  the  shreds  of  potato  will  float,  while  a  white  substance  A^ill  settle 
to  the  bottom  of  the  basin.  Explain  that  this  substance  is  starchy  and 
that  our  great-grandmothers  used  this  method  to  make  starch  for 
laundering. 

9.  Place  a  small  drop  of  the  wet  potato  starch  upon  a  glass  slide 
and  examine  it  with  a  power  of  at  least  50  diameters.  Notice  that  the 
starch  grains  appear  like  oyster  shells.  Examine  also  some  corn  starch 
and  notice  that  each  grain  looks  like  an  irregular  cube  with  a  star-shaped 
center.     Sketch  the  starch  grains. 

10.  BoQ  some  starch  and  notice  that  it  swells  and  forms  a  jellylike 
paste. 

Iodine  turns  starch  blue.  Apply  a  drop  of  the  tincture  of  iodine  to 
the  starch  and  notice  the  blue  color.  Apply  it  to  bread,  cake,  flour, 
etc.  Notice  the  blue  color,  showing  that  they  all  contain  starch. 
Notice  that  meat  does  not  respond  to  the  test. 

11.  Show  specimens  of  sugar.  Brown  sugar  is  the  impure  form, 
while  granulated  sugar  is  the  pure  crj'stallized  form.  Show  some  sugar 
scraped  from  the  outside  of  raisins  and  explain  that  this  is  glucose  or 
grape  sugar,  and  that  all  sugar  and  starch  must  be  changed  into  this 
form  before  it  can  be  used  by  the  body. 


32  APPLIED   PHYSIOLOGY 

12.  Burn  some  bread  or  meat  and  save  the  ashes.  The  ashes 
represent  the  mineral  part  of  food,  and  consist  mainly  of  lime,  salt, 
soda,  potash,  and  iron. 

13.  Show  diffusion  by  tying  a  piece  of  parchment  over  the  end  of  a 
larse  s^lass  tube.  Fill  the  tube  with  salt  and  water  and  immerse  it  in 
ajar  of  fresh  water.  In  a  little  while  the  liquid  will  rise  in  the  tube, 
while  the  water  in  the  jar  will  begin  to  taste  salt.  The  process  will 
continue  until  the  water  in  the  tube  and  in  the  jar  are  of  equal  saltness. 
If  the  water  in  the  jar  were  renewed,  all  the  salt  could  be  extracted 
from  the  tube. 

14.  Show  the  affinity  between  acids  and  alkalies  by  dropping  soda 
in  vinegar.  Notice  that  the  mixture  boils  and  foams,  and  both  sub- 
stances become  changed.  Drop  some  soda  in  water  and  it  simply 
dissolves  and  forms  a  solution. 

15.  Drop  a  pinch  of  baking  soda  in  a  small  cup  of  water.  Then 
stir  in  some  dilute  hydrochloric  acid,  drop  by  drop,  until  the  mixture 
ceases  to  bubble.  Taste  the  mixture  and  notice  that  it  is  salt.  Ex- 
plain that  the  hydrochloric  acid  and  the  soda  have  formed  a  chemical 
combination  and  each  has  neutralized  the  other.  The  new  substance 
formed  is  chloride  of  sodium  or  common  salt. 

REVIEW  TOPICS 

1.  Define  and  name  \\\^ proxhnate principles. 

2.  Describe  water  and  define  a  solution. 

3.  Describe  albumin. 

4.  Describe  diffusion. 

5.  T)Qscx\hQ  ptitrefaction. 

6.  Describe  nucleo-albumin^  and  its  relation  to  iron. 

7.  Describe /^/j"  and  oils. 

8.  Describe  an  emulsion. 

9.  Describe  saponification. 

10.  Describe  starch,  sugar,  and  wood. 

1 1 .  Describe  salt. 

12.  Describe  lime. 

13.  'DQ^cxihQ  t\\Q  alkalies. 

14.  Define  chemical  action  and  chem,ical  affinity. 

15.  Name  some  chemical  actions  in  the  body. 


CHAPTER   III 


OXIDATION 


^5    <;: 


Oxygen  iniheaif- 


37.  The  nature  of  burning  or  oxidation.  —  In  addition  to 
the  substances  taken  in  as  food,  the  body  is  continually 
taking  in  oxygen  by  the  breath.     The  air  which  is 
breathed  is  four  fifths  nitrogen  gas  and  one  fifth 
oxygen  gas.     When  air  is  fed  to  fuel  in  the  hot 
fire  box  of  a  boiler,  burning  takes  place.     Burn- 
ing is   a    chemical  process.     Oxygen  unites  with 
the  carbon  and  the  hydro- 
gen  of  the  wood,  so  that 
both    the    wood    and    the 
oxygen    disappear.       The 
carbon    and    part   of    the 
oxygen  form  carbojiic  acid 
gas.       The   hydrogen  and 
the    rest    of    the    oxygen 
form    water.       Both    sub- 
stances pass  off  in  the  smoke, 
the  fnineral  part  of  the  wood. 

By  the  burning,  heat  and  a  flame  are  produced.  The 
heat  can  be  used  to  make  steam  which  will  drive  an 
engine  and  do  work.     Burning  is  called  oxidation. 

38.  Oxidation  within  the  body.  —  The  body  also  is  an 
e^tgine,  —  self-regulating  and  self-sustaining.  The  oxygen 
which  is  breathed  into  the  body  slowly  burns  food  and 
the  cells,  just  as  it  oxidizes  the  wood  under  the  boiler  of  an 

OV.   PHYSIOL.  —  3  33 


^ 


Diagram  of  burning  or  oxidation  in  a 
stove. 


What  is  left  as   ashes  is 


34  APPLIED   PHYSIOLOGY 

engine.  The  process  goes  on  so  slowly  that  no  flame 
is  produced,  but  the  same  amount  of  heat  is  produced  as 
though  the  same  substances  were  burned  in  a  furnace. 
Some  of  this  heat  is  used  to  warm  the  body,  and  some 
is  changed  to  power  which  enables  the  body  to  do  work, 
either  of  motion,  or  of  manufacturing  the  various  products 
of  the  body  or  of  thought.  Oxidation  is  an  essential 
process  of  life ;  when  it  ceases  for  an  instant  life  ends. 
When  the  air  is  cut  off  from  the  body  for  only  a  minute, 
a  great  feeling  of  suffocation  comes  on,  and  within  two 
or  three  minutes  the  body  dies. 

Oxidation  goes  on  in  each  cell,  but  especially  in  the 
cells  of  the  lungs  and  liver.  It  is  a  process  of  life,  and 
in  a  living  cell  it  can  be  hastened  or  retarded  according 
to  the  needs  of  the  body. 

By  the  oxidation  within  the  cells  of  the  body,  carbonic 
acid    gas,  water,  and  ashes  are  formed,  as  in  a  furnace. 

39.  Oxidation  of  albumin.  —  An  ounce  of  albumin  is 
completely  oxidized  by  an  ounce  and  a  half  of  oxygen. 
The  ashes  which  are  produced  are  partly  the  sidpJmr  of 
the  albumin  and  partly  the  nitrogen,  which  holds  some 
of  the  carbon,  hydrogen  and  oxygen,  combined  in  a 
solid  called  nrea.  Urea  must  be  given  off  by  the  kid- 
neys and  skin  as  fast  as  it  is  formed.  When  there  is 
not  enough  oxygen  to  burn  the  albumin  entirely,  other 
substances  resembling  urea  are  formed,  just  as  a  stove 
smokes  instead  of  burning  brightly  when  the  draft  is 
closed.  Some  of  these  substances  are  very  poisonous. 
The  albumin  of  the  living  cells  must  be  oxidized  and 
replaced  continually.  Much  of  the  albumin  of  the  food 
is  oxidized  before  it  reaches  the  cells. 

40.  Oxidation  of  fat.  —  An  ounce  of  fat  is  completely 
oxidized  by  three  ounces  of  oxygen.     So  it  will  produce 


OXIDATION 


35 


twice  as  much  heat  as  the  same  amount  of  albumin,  and 
is  thus  a  good  food  for  cold  weather.  It  leaves  no  ashes 
behind,  for  it  contains  no  mineral  matter. 

41.  Oxidation  of  sugar.  —  An  ounce  of  sugar  is  com- 
pletely oxidized  by  one  and  one  iifth  ounces  of  oxygen. 
So  it  produces  only  about  half  as  much  heat  as  fat.  It 
is  much  more  easily  oxidized  than  fat  or  albumin.  When 
the  three  substances  are  mixed  together  as  they  are  in  the 
body,  the  oxygen  will  go  to  the  sugar  in  preference  to 
the  fat  or  albumin,  and  the  latter  two  substances  being 
unburned  will  accumulate  in  the  body.  Thus  sugar  is 
said  to  be  fattening.  The  water  and  the  minerals  of  the 
body  cannot  be  oxidized,  but  enter 
and  leave  the  body  unchanged. 

42.  Reconstruction  of  living  mate- 
rial by  plants.  —  In  every  animal  the 
living  cells  are  continually  uniting 
with  the  oxygen  of  the  air  and  giving 
out  carbonic  acid  gas,  water,  and  min- 
eral matters.  From  these  waste  mat- 
ters plants  reconstruct  the  substances 
which  were  oxidized  in  the  body. 
The  first  substance  produced  seems 
to  be  starch,  and  from  it  as  a  basis  all 
other  parts  of  the  plant  and  of  ani- 
mals are  built  up. 

The  plant  cells  which  contain 
green   coloring  matter  called  chloro-    _^,      ^  „  . 

^  ^  Chlorophyll  in  pond  algae. 

phyll,  are  set  apart^  for  the  special  ^  chlorophyll  arranged  in 
work  of  reconstructing  starch   from        a  spiral. 

•  T        ,  ^       .    1        ,_         .  .  b   The  clear  body  of  the  cell. 

oxidized  material.     To  them  the  sap 

brings  water  from  the   soil,  and  carbonic    acid  gas  from 

the    air.       In  the  chlorophyll  these  substances  are  recon- 


36 


APPLIED   PHYSIOLOGY 


Carbonic  Kcid  Gets 

in  the  airaoinj 

into  theteaf 


structed    into   starch.      Using   starch    as    a   basis,    plants 
construct  fat  and  albumin  and  all  other  substances  found 

in  the  plant. 

43.    The    sun*s    work 

in  reconstructing  living 

material.  —  When  oxygen 
unites  with  the  carbon  and 
hydrogen  of  the  burning  sub- 
stances, heat  and  energy  are 
given  out.  Just  as  much 
heat  and  force  must  be  used 
in  tearing  away  the  oxygen 
as  was  given  out  during  the 
oxidation.  The  sun  furnishes 
this  heat  and  force.  The 
chlorophyll  acting  as  the  ma- 
chine and  using  the  sun's  rays 
for  power,  frees  most  of  the 
oxygen  from  the  carbonic 
acid  gas  and  water,  and  gives 
it  back  to  the  air.  At  the 
same  time  it  unites  the  re- 
maining oxygen  with  the  car- 
bon and  hydrogen  to  form  living  starch.  Thus  the  real  work  of  con- 
struction is  done  by  the  sun.  When  the  starch  is  oxidized,  oxygen  goes 
back  to  the  hydrogen  and  carbon,  and  the  same 
amount  of  heat  is  given  off  as  was  taken  from 
the  sun  when  starch  was  formed. 

The  heat  of  oxidation  can  be  traced  back  to  the 
sun's  heat  stored  up  by  living  beings  or  beings 
once  alive.  All  the  carbon  of  a  tree  is  the  car- 
bonic acid  gas  of  the  air  with  its  oxygen  taken 
away  by  the  sun's  force  acting  through  chloro- 
phyll. Coal  is  the  carbon  of  trees  changed  in 
form  during  ages  of  burial. 


Diagram  of  the  restoration  of  oxygen  to 
the  air  after  oxidation,  and  of  the  rebuilding 
of  burned  material  into  living  forms. 


Diagram  of  the  stream 
of  material flowingthrough 


44.    Conservation   of   energy.  —  The 

energy  of  the   sun  s   lie  at   expended   upon   the   plants   in 


OXIDATION  37 

bygone  ages  was  conserved  in  the  coal,  and  now  can  be 
made  to  appear  again  ?iS  force  in  a  steam  engine.  This 
force  may  run  an  electric  dynamo,  and  the  electricity  can 
be  transported  silently  over  miles  of  wire,  to  appear  as  light 
rivaling  its  original  source,  the  sun.  Through  all  its 
changes  the  original  energy  is  preserved. 

Observation  of  the  three  facts,  (i)  the  heat  of  the  sun 
acting  through  plants  to  tear  the  oxygen  from  the  carbon 
and  hydrogen,  (2)  the  reunion  of  the  substances  in  oxi- 
dation with  the  development  of  the  original  heat  of  the 
sun,  and  (3)  the  various  forms  of  power  into  which  the 
energy  can  be  changed,  has  given  rise  to  the  principle  that 
any  fonn  of  energy  can  be  changed  into  anotJier  fonn  without 
loss.     This  principle  is  called  the  conservation  of  energy. 

This  principle  is  exemplified  in  the  human  body.  The 
energy  for  the  work  done  by  the  body  is  the  heat  derived 
from  the  oxidation  of  its  food. 

45.  Relation  of  plants  to  animals. — The  oxygen  of  the 

air  would  all  be  used  up  in  a  few  years  if  it  were  not  continually  torn 
away  by  plants  from  its  combinations  in  carbonic  acid  gas  and  water. 
The  carbon  and  hydrogen  would  also  disappear ;  but  the  sun  and 
chlorophyll  continually  renew  the  supply  both  of  food  and  of  oxygen. 
Thus  there  is  a  stream  of  material  flowing  from  lifeless  soil  and  air.  It 
becomes  alive  in  the  plant  and  again  in  the  animal,  and  then  is  suddenly 
oxidized  to  a  lifeless  form,  and  given  back  to  the  soil  and  air,  only  to 
repeat  the  round  of  life.  Plants  build  up  living  material  which  animals 
use  as  food  and  then  oxidize  back  to  the  form  in  which  it  existed  before 
the  plant  touched  it.  Plants  give  off  oxygen  which  supports  animal 
life.     Each  lives  upon  what  the  other  discards. 

46.  Organic  substances.  —  Substances  which  are  built 
up  by  living  beings  are  called  organic.  Thus  the  plant 
takes  carbon  from  the  carbonic  acid  gas  in  the  air,  and 
builds  it  up  into  an  organic  substance,  which  forms  part  of 
the  plant. 


38  APPLIED   PHYSIOLOGY 

47.  Difference   between   plants    and    animals.  —  (i)  The 

ability  to  live  upon  the  ordinary  waste  products  of  animal  life,  or,  in  other 
words,  to  reconstruct  organic  matter  out  of  crude  ?ninerals  and  gases ^  is 
a  distinguishing  mark  of  a  plant.  On  the  other  hand  an  animal  always 
requires  organic  food,  and  cannot  live  upon  the  soil  and  air.  Yet  the 
lowest  animals  very  closely  resemble  plants,  and  owing  to  the  difficulty 
of  ascertaining  the  true  source  of  their  food  the  position  of  some  living 
bodies  is  still  a  matter  of  dispute. 

(2)  In  animals  the  cells  are  bound  together  by  strings  of  connective 
tissue,  which  is  an  albuminous  substance  of  soft  consistency.  In  plants 
the  substance  between  the  cells  has  the  composition  of  starch  (see 
p.  27).  It  is  a  hard  andfir7)i  substance,  and  gives  the  rigid  strength  to 
the  plant  or  tree.  The  outsides  of  the  plant  cells  often  have  a  thick 
coating  of  the  same  substance.  When  it  is  deposited  in  so  great  an 
amount  as  almost  to  replace  the  cells  the  substance  forms  wood.  Yet 
in  some  plants  it  is  entirely  absent,  so  that  the  distinction  applies  only 
to  higher  forms  of  life,  where  other  distinctions  between  plants  and 
animals  are  more  obvious. 

(3)  Most  animals  have  the  power  of  voluntary  motion,  while  most 
plants  2lX^  fixed  to  one  spot.  Yet  some  animals,  as  the  coral,  have  no 
more  motion  than  a  flower  which  opens  and  closes  during  the  day.  On 
the  other  hand  some  water  plants  are  continually  moving  about  by 
means  of  vibrating  hairs  projecting  from  their  bodies. 

Some  plants  also  move  if  irritated.  The  plant  called  Venus^s  flytrap 
has  stiff,  toothed  leaves,  hinged  together  in  twos  so  as  to  open  and  shut 
like  a  rat  trap.  When  a  fly  alights  upon  the  open  leaf  it  suddenly  closes 
upon  the  insect,  crushing  it  to  death.  This  plant  exhibits  more  move- 
ment responsive  to  a  slight  irritation  and  directed  to  a  distinct  purpose 
than  many  true  animals. 

(4)  Most  animals  have  a  digestive  tube,  while  plants  have  no  organs 
of  digestion,  unless  the  leaves  can  be  called  such.  Yet  in  some  animals, 
as  the  ameba,  the  body  looks  nearly  the  same  throughout. 

(5)  Most  plants  2,x^  greefi  in  color,  from  the  presence  of  chlorophyll. 
Yet  many  plants,  as  toadstools,  are  destitute  of  chlorophyll. 

48.  Source  of  life.  —  In  the  oxidation  and  reconstruction 
of  animals  and  plants  no  new  life  is  created.  Lifeless 
miterial  is  endowed  with  life  by  material  already  living, 
and  in  its  turn  the  new  material  imparts  life.     The  same 


OXIDATION  39 

life  continues  through  all  the  changes  of  the  body, 
although  not  a  single  particle  of  the  original  body  may 
remain.  The  body  is  but  the  house  in  which  life  resides. 
The  original  source  of  life  itself  has  never  been  found. 
The  Bible  gives  the  only  known  origin  of  life : 

"And  God  said,  Let  the  earth  bring  forth  grass,  the 
herb  yielding  seed,  and  the  fruit  tree  yielding  fruit  after 
his  kind,  whose  seed  is  in  itself,  upon  the  earth :  and  it 
was  so. 

"  And  the  earth  brought  forth  grass,  and  herb  yielding 
seed  after  his  kind,  and  the  tree  yielding  fruit,  whose 
seed  was  in  itself,  after  his  kind :  and  God  saw  that  it  was 
good."  —  Gen.  i  :  11-12. 

SUMMARY 

1.  Oxygen    unites  with  carbon  and    hydrogen,   and    pro- 

duces heat.  The  process  is  called  burning  or  oxida- 
tion.    A  steam  engine  transforms  heat  into  work. 

2.  Oxygen  from  the  air  is  continually  entering  the  body. 

3.  Within    the   body   it   is    continually   uniting   with   the 

albumin,  fat,  and  sugar,  and  producing  heat,  some  of 
which  is  transformed  into  work.  This  is  the  essential 
process  of  life. 

4.  By  oxidation,  the  albumin,  fat,  and  sugar  become  car- 

bonic acid  gas,  water,  and  urea,  and  are  given  off 
from  the  body. 

5.  The  green  coloring  matter  of  plants  forms  the  machine, 

by  means  of  which  the  sun's  heat  tears  the  oxygen 
away  from  the  carbonic  acid  gas  and  water  and 
forms  organic  substances  again. 

6.  Plants  prepare  food  for  animals,  and  animals  prepare 

food  for  plants. 


40  APPLIED   PHYSIOLOGY 

7.  All  through  the   oxidation   and  reconstruction   of   the 

body   life    remains   the    same,    and   no    new   life    is 
created. 

8.  The   Bible  gives  the  only  known  explanation  of  the 

origin  of  life. 

DEMONSTRATIONS 

16.  Lower  a  lighted  candle  into  a  wide-mouthed  bottle.  When  it 
goes  out  pour  in  a  little  lime  water,  then  stop  the  mouth  of  the  bottle 
and  shake  it.  The  water  becomes  milky,  showing  that  carbonic  acid 
gas  has  been  produced.  By  means  of  a  straw  or  glass  tube  blow  a 
little  air  through  a  cup  of  lime  water  and  notice  that  again  the  water 
becomes  milky.     This  shows  the  carbonic  acid  of  the  breath. 

17.  Hold  a  lighted  match  under  a  cold  tumbler.  In  a  few  seconds 
drops  of  moisture  will  condense  upon  the  inside  of  the  glass.  Explain 
that  the  water  is  formed  by  the  union  of  the  hydrogen  of  the  match 
stick  with  the  oxygen  of  the  air. 

REVIEW  TOPICS 

1.  Describe  oxidation  and  its  products. 

2.  Show  how  oxidation  takes  place  in  the  body. 

3.  Describe  the  oxidation  of  each  proximate  principle. 

4.  Describe  the  series  of  changes  by  which  the  oxidized 

materials  of  the  body  are  again  built  up  into  living 
bodies. 

5.  Define  and  illustrate  co7tservation  of  energy^  and  apply 

it  to  man's  body. 

6.  Define  organic  bodies. 

7.  Give  points  of  difference  between  pla^its  and  animals. 

8.  Give  the  only  known  source  of  life. 


CHAPTER    IV 


FERMENTATION  AND   ALCOHOL 


49.  Production  of  alcohol  and  vinegar.  —  Unless  great 
care  is  taken  to  preserve  it,  a  weak  solution  of  sugar  soon 
turns  to  vinegar ;  a  stronger  solution 
turns  to  alcohol^  while  a  thick,  sirupy 
solution  remains  unchanged.  Every- 
where there  are  scattered  minute  living 
germs  which,  falling  into  a  moderately 
strong  solution  of  sugar  in  water,  grow 
and  produce  oval  plants  each  about 
^Q^QQ  inch  in  length.  A  collection  of 
these  plants  is  called  yeast.  By  their 
growth  and  multiplication  they  change 
sugar  to  alcohol  and  carbonic  acid  gas. 
The  gas  bubbles  up  through  the 
liquid  and  makes  a  froth  upon  the  top, 
while  the  alcohol  remains  in  the  water. 
If  only  a  small  quantity  of  sugar  is  present  another  kind 
of  germ  from  the  air  enters  and  grows,  becoming  tiny 
rodlike  plants,  each  about  -j-q^qq  inch  in  length.  By 
their  growth  and  multiplication  they  change  the  alcohol 
to  vinegar.     They  collect  in  a  mass  called  the  mother  of 


Yeast  plant  cells  (X  500). 


Vinegar. 


Boiling  destroys  both  the  yeast  and  vinegar  germs.  If 
the  sugar  and  water  are  boiled  and  at  once  sealed  tightly, 
so  that  new  germs  cannot  enter,  the    solution  will   keep 

41 


42  APPLIED   PHYSIOLOGY 

for  an  indefinite  time.  Fruit  when  boiled  and  at  once 
sealed  in  air-tight  cans  will  keep  unchanged  for  a  long 
time.  If  there  is  a  great  deal  of  sugar  present  no  germs 
at  all  will  grow,  and  the  solution  will  keep  indefinitely. 
This  is  why  fruit  can  be  preserved  in  open  jars  if  a  great 
deal  of  sugar  is  used. 

50.  Fermentation.  —  Changing  sugar  to  alcohol  or  vine- 
gar is  an  example  of  fenneiitatioji.  A  substance  which 
can  change  the  composition  of  other  bodies  without  losing 
its  own  identity  or  characteristics  is  a  ferment.  A  very 
small  amount  of  a  ferment  can  change  a  very  large  amount 
of  another  substance. 

A  very  small  amount  of  yeast  will  cause  an  indefinite 
amount  of  sugar  to  become  changed  to  alcohol  or  vinegar. 
At  the  same  time  the  yeast  may  not  grow  weaker,  but 
on  the  contrary  may  become  stronger  than  at  first.  In  the 
same  way  a  small  amount  of  "  mother "  will  change  a 
large  amount  of  weak  alcohol  to  vinegar,  and  itself  will 
greatly  increase  in  amount. 

51.  Kinds  of  ferments.  —  Nature  uses  many  ferments  in  her 
actions.  Some  are  living  beings  and  some  are  lifeless  substances.  The 
chief  part  of  the  digestion  of  food  is  done  by  lifeless  ferments.  Fer- 
mentation is  commonly  spoken  of  as  a  process  of  decay,  but  the 
common  process  of  decay  or  rot  is  in  itself  only  a  special  kind  of  fer- 
mentation. Ordinary  decay  is  caused  by  a  living  beins^  like  the 
vinegar  germ.  By  its  growth  and  multiplication  it  softens  and  liquefies 
the  albumin  of  animal  and  vegetable  matter.  This  process  is  called 
putrefaction  (.see  p.  24).  Some  of  the  matter  passes  off  as  foul  smell- 
ing gases,  while  the  liquid  part  soaks  into  the  soil.  Putrefaction  is 
nature's  way  of  giving  dead  bodies  back  to  the  soil  and  air  so  that 
plants  can  build  them  into  useful  forms  again. 

Yeast  germs  are  found  everywhere,  but  they  are  often  grown  in  wet 
meal  or  flour.  The  mass  is  then  dried  in  cakes  and  .sold  as  yeast. 
When  a  small  piece  is  added  to  sugar  and  water  it  starts  alcoholic  fer- 
mentation at  once.     Alcoholic  fermentation  only  is  usually  meant  when 


FERMENTATION  AND   ALCOHOL  43 

the  term  fermentation  is  used  alone.  An  adjective  signifying  the 
special  form  of  fermentation  is  used  to  indicate  any  other  form  than 
the  alcoholic.  Thus  there  is  acetous  or  vinegar  fermentation,  and 
putrefactive  fermentation. 

52.  Bread  making.  —  By  the  growth  of  yeast  plants  in 
bread  dough  some  of  the  sugar  in  the  flour  is  changed 
to  carbonic  acid  gas  and  alcohol.  The  gas  bubbles  up 
through  the  dough,  making  it  porous  and  Hght.  When 
the  bread  is  baked,  alcohol  is  driven  off  and  the  yeast 
germs  are  killed  by  the  heat.  They  are  eaten  with  the 
bread,  for  they  are  perfectly  wholesome.  When  germs 
of  vinegar  or  other  acid  fermentations  enter  the  bread 
and  grow,  the  bread  sours.  These  germs  grow  more 
slowly  than  yeast,  and  usually  do  not  have  time  to  de- 
velop. But  if  the  bread  is  a  long  time  in  rising,  they 
may  grow  and  make  the  bread  sour. 

53.  Fermented  drinks.  —  Man  uses  the  same  process  to 
produce  drinks,  which  are  erroneously  supposed  by  many  to 
act  as  a  beneficial  food,  quenching  thirst  and  giving  strength 
to  the  body  and  power  and  joy  to  the  mind.  There  are 
three  classes  of  such  drinks,  all  containing  alcohol  as  an 
essential  part. 

54.  Malt  liquors.  —  The  commonest  form  is  what  is 
known  as  malt  liquors.  Barley  and  other  grain  are  mois- 
tened and  permitted  to  sprout  until  the  new  stalk  is  about 
one  half  inch  in  length.  This  changes  much  of  the  starch 
of  the  grain  to  sugar.  The  sugar  is  dissolved  out  by  boil- 
ing the  grain  along  with  hops  and  various  other  flavoring 
substances.  Then  yeast  is  added  and  alcoholic  fermen- 
tation occurs.  The  result  is  beer.  It  contains  from  one 
to  ten  per  cent  of  alcohol.  Much  of  the  flavoring  which 
is  often  added  to  it  is  not  only  injurious,  but  actually 
poisonous. 


44  APPLIED    PHYSIOLOGY 

55.  Wines. — The  second  class  of  alcoholic  liquors  is 
wine.  The  juice  is  squeezed  from  grapes,  blackberries,  or 
some  other  fruit  rich  in  sugar.  Germs  of  alcoholic  fer- 
mentation from  their  skins  and  the  air  set  up  ferrrientation 
in  the  juice  and  produce  wine.  Certain  localities  and  cellars 
contain  special  kinds  of  germs  which  produce  a  peculiar 
flavor  in  the  wine  fermenting  in  that  localit3^  In  this  way- 
different  kinds  of  wine  are  produced.  Wine  contains  from 
five  to  fourteen  per  cent  of  alcohol.  Fourteen  per  cent  of 
alcohol  in  the  juice  kills  the  germs  and  stops  the  fermenta- 
tion. So  wine  cannot  contain  more  than  that  amount  of 
alcohol  unless  more  is  added. 

56.  Distilled  liquors  or  spirits.  —  The  third  class  of 
alcoholic  drinks  is  spirits,  or  distilled  liquors.  Alcohol 
boils  at  a  temperature  of  170°  F.,  while  water  boils  at 
212°  F.  Thus  when  a  wine,  or  beer,  or  any  other  alco- 
holic solution  is  heated  its  alcohol  will  be  changed  to 
steam  very  rapidly,  while  the  water  will  evaporate  slowly. 
Therefore  the  steam  will  contain  a  larger  proportion  of 
alcohol  than  the  original  liquor.  This  fact  is  put  to  use  in 
separating  alcohol  from  the  solution  in  which  it  was  pro- 
duced. The  steam  is  conducted  through  a  coil  of  pipe 
kept  cool  by  running  water.  Its  temperature  is  lowered 
and  it  is  changed  back  to  a  liquid  form.  This  new  liquid 
is  whisky,  or  brandy,  or  other  spirituous  liquor,  according 
to  the  substance  used  in  its  manufacture.  The  process 
of  its  manufacture  is  called  distillation.  Spirituous  liquors 
are  about  one  half  alcohol. 

57.  Description  of  alcohol.  —  If  the  process  of  distillation 
is  repeated  the  alcohol  which  passes  over  is  still  freer  from 
water,  until  after  three  or  four  distillations  it  is  almost 
pure.  It  is  then  a  clear,  colorless  liquid  like  water.  It  has 
a  sharp,  sweetish  taste  and  a  peculiar  odor.     It  causes  a 


FERMENTATION  AND   ALCOHOL  45 

severe  smarting  sensation  when  applied  to  a  raw  sore  or  to 
the  eye  or  mouth.  It  is  a  valuable  and  useful  article  when 
rightly  used  in  the  manufactures  and  arts.  But  men  have 
formed  the  bad  habit  of  liking  its  taste  and  the  feelings 
which  it  produces.  They  drink  strong  drink  solely  for 
the  sake  of  the  alcohol  which  it  contains.  The  alcohol 
has  an  injurious  effect  upon  every  part  of  the  body. 
These  effects  will  be  described  in  detail  as  each  organ  is 
studied. 

58.  Kinds  of  alcohol.  —  Alcohol  is  the  name  for  a  series  of  sub- 
stances formed  out  of  the  same  elements,  but  varying  in  composition, 
yet  alike  in  essential  properties.  The  simplest  form  is  called  ?nethyl 
alcohol,  or  wood  spirits,  and  is  formed  by  distilling  wood.  It  has  an 
unpleasant  odor  and  taste,  but  nearly  the  same  properties  as  common 
alcohol.  It  is  much  used  in  manufacturing  and  in  the  arts,  as  a  substi- 
tute for  common  alcohol,  on  account  of  its  cheapness. 

The  next  form,  called  ethyl  alcohol,  is  the  common  alcohol  made 
from  wine,  beer,  etc. 

The  fifth  in  the  series  is  called  aniyl  alcohol  or  fusel  oil,  from  the 
German  fusel,  bad  liquor.  It  has  a  bad  odor  and  nauseous  taste,  and 
is  far  more  poisonous  than  common  alcohol.  It  is  formed  in  con- 
siderable quantities  when  potatoes  are  fermented.  But  if  the  whisky 
stands  for  some  years,  the  fusel  oil  becomes  changed  to  ordinary 
alcohol. 

59.  What  becomes  of  alcohol  in  the  body.  —  When  taken 

into  the  stomach,  alcohol  passes  into  the  blood  with  great 
rapidity.  The  body  has  the  power  of  rapidly  disposing  of 
it  either  by  giving  it  off,  or,  more  probably,  by  oxidizing  it 
to  carbonic  acid  and  water,  and  thus  destroying  it.  At 
any  rate,  little  or  no  alcohol  can  be  found  in  any  part 
of  the  body  or  in  its  waste,  no  matter  how  much  is  taken. 
But  its  oxidation  takes  place  in  an  irregular  way  which  is 
injurious  to  the  body. 


46  APPLIED   PHYSIOLOGY 

60.  Effects  of  alcohol.  —  (i)  Prevents  fermentation  and 
decay.  —  While  alcohol  is  the  product  of  fermentation,  it 
has  the  power  to  prevent  fermentation.  The  germs  pro- 
ducing alcohol  will  not  grow  when  alcohol  is  present  in  the 
proportion  of  14  per  cent.  Germs  of  decay  will  grow  in  a 
much  larger  percentage  of  alcohol,  but  no  germs  will  grow 
in  a  solution  of  one  half  alcohol.  This  fact  is  put  to  use 
in  preserving  specimens  of  animals  and  vegetables  in 
museums,  by  placing  them  in  spirits  or  alcohol.  Since 
decay  is  dependent  upon  germs,  the  alcohol,  by  preventing 
their  growth,  prevents  decay.  It  can  also  prevent  the 
digestive  ferments  from  acting  upon  food. 

(2)  Extracts  water  from  tissues.  —  Water  and  alcohol 
mix  very  readily.  An  uncorked  bottle  of  alcohol  takes  up 
water  from  the  air,  and  so  becomes  weakened.  W^hen 
alcohol  is  in  contact  with  a  wet  substance,  it  appropriates 
some  of  its  water,  and  the  substance  then  shrivels  and 
becomes  firmer.  Strong  whisky  can  produce  the  same 
result  in  the   body  to  a  Hmited  extent. 

(3)  Hardens  tissues. — Alcohol  also  hardens  many  ani- 
mal and  vegetable  substances  by  extracting  their  water  and 
by  coagicla ting  t]\Q\r  albumin.  In  museums  this  fact  is  put 
to  use  in  hardening  soft  and  delicate  specimens  of  animals 
and  vegetables,  so  they  may  be  preserved  and  examined 
safely.  It  is  not  probable  that  this  action  occurs  in  the 
body,  for  nature  pours  out  an  abundance  of  water  to  dilute 
the  irritating  alcohol. 

Within  the  body  the  effect  of  extracting  water  from  the 
tissues  and  of  hardening  albumin  is  to  produce  a  smarting 
sensation  which  shows  that  the  organs  are  being  injured. 
There  would  be  no  limit  to  this  action  and  death  would 
soon  take  place  if  nature  did  not  provide  means  for  a 
partial  protection  against  the  substance.     When  any  part 


FERMENTATION  AND   ALCOHOL  4/ 

of  the  body  is  harmed,  nature  pours  an  abundance  of 
water  over  the  injured  spot,  so  as  to  dilute  and  wash  away 
the  irritating  substance,  just  as  she  pours  out  tears  to  wash 
a  speck  of  dirt  away  from  the  eye.  Alcohol  attracts  water 
to  itself,  and  thus  its  power  to  do  harm  is  greatly  lessened. 
But  this  protection  is  only  partial.  If  only  a  small  amount 
of  strong  drink  is  used  steadily  for  some  time,  nature 
becomes  exhausted  in  her  efforts  of  defense.  Thus,  while 
some  exceptionally  strong  men  seem  able  to  use  a  large 
amount  of  strong  drink  with  little  harm,  most  men  are 
greatly  harmed  by  the  smallest  amounts. 

61.  Cause  of  thirst  for  alcohol.  —  The  property  of  taking 
away  water  from  substances  which  it  touches,  accounts  in  part  for  the 
failure  of  alcoholic  drinks  to  satisfy  thirst.  A  dry  state  of  the  surface 
of  the  lining  of  the  mouth  gives  rise  to  thirst.  If  this  lining  is  deprived 
of  water  by  an  alcoholic  drink,  the  sense  of  thirst  still  remains,  although 
the  rest  of  the  body  is  supplied  with  water.  Moreover,  this  lining  is 
somewhat  injured  by  the  alcohol  of  every  drink,  and  to  soothe  the  irri- 
tation another  drink  is  needed.  So  the  thirst  goes  on,  growing  stronger 
with  every  drink. 

When  he  begins,  no  drunkard  expects  to  use  strong  drink,  or  to 
drink  more  than  a  glass  or  two  at  a  time,  but  his  thirst  always  deceives 
him,  and  the  momentary  relief  which  drink  gives  him  is  only  a  deceitful 
addition  to  his  thirst. 

62.  Adulteration  of  alcoholic  drinks.  —  The  manufacture  of 
pure  alcoholic  liquors  is  a  slow  and  expensive  process.  So  cheap  imi- 
tations are  made  which  closely  resemble  the  real  article  in  taste  and 
appearance.  Beer  is  often  made  from  cheap  rye  or  corn  and  quassia, 
instead  of  barley  and  hops.  Its  fermentation  is  often  hastened  by  an 
excess  of  yeast,  and  then  the  product  is  preserved  by  adding  salicylic 
acid  or  other  substances  which  destroy  the  yeast. 

Whisky  and  brandy  are  also  much  adulterated.  All  kinds  are  alike 
in  having  a  large  amount  of  alcohol.  In  fact,  the  cheaper  kinds  of 
whisky  and  brandy  contain  the  most  alcohol. 

Often,  instead  of  good  grain  or  fruit,  rotten  fruit,  peelings,  and  refuse 
of  all  kinds  are  used  in  making  liquors.     When  distilled  and  treated 


48  APPLIED   PHYSIOLOGY 

with  flavorings,  a  drink  is  produced  which  an  expert  chemist  can 
scarcely  distinguish  from  genuine  liquor,  and  yet  its  evil  effects  are 
notoriously  greater. 

63.  Temperance  drinks.  —  Strictly  speaking,  water  is 
the  only  temperance  drink,  for  all  kinds  of  flavored  and 
fermented  drinks  are  designed  only  to  please  the  taste  and 
not  to  fill  a  want  of  the  body.  The  use  of  any  except  water 
is  a  form  of  intemperance,  but  those  which  contain  alcohol 
are  especially  harmful. 

Cider,  root  beer,  and  ginger  ale,  and  other  "  homemade  " 
drinks  which  are  ''worked"  or  fermented,  all  contain 
alcohol,  and  should  be  classed  as  strong  drink.  These 
drinks  are  particularly  bad,  for  their  use  may  lead  one  to 
indulge  in  stronger  drinks. 

SUMMARY 

1.  A  sirupy  solution  of  sugar  will  not  become  sour,  but 

will  "  preserve  "  fruit  from  spoiling. 

2.  Sugar  in  a  weak  solution  becomes  alcohol. 

3.  The  change  is  produced  by  the  growth  of  microscopic 

plants  c3i[\Qd  j/east. 

4.  Sugar  in  weaker  solution  becomes  vinegar. 

5.  The  change  is  produced  by  a  collection  of  microscopic 

rodhke  plants  which  form  the  "mother"  of  vinegar. 

6.  Changing  sugar  to  alcohol  or  vinegar  is  fermentation. 

7.  Wine  is  made  by  fermenting  fruit  juice,  and  beer  is 

made  by  fermenting  a  solution  of  sprouting  grain. 

8.  Distilled  liquors  are  made  by  boiling  fermented  liquors 

and  collecting  the  vapor. 

9.  Alcohol  prevents  decay  by  killing   the  germs  which 

produce  rotting. 
10.    Alcohol  takes  water  away  from  other  substances  and 
then  hardens  and  shrivels  them. 


FERMENTATION   AND   ALCOHOL  49 

11.  Alcohol   disappears   very   rapidly  after   being   taken 

into  the  body. 

12.  Alcohol  takes  water  from   the  lining  of  the  mouth 

and  produces  thirst. 

DEMONSTRATIONS 

18.  Show  fermentation  by  setting  aside  a  bottle  containing  a  little 
molasses  in  water.  In  a  few  days  bubbles  will  rise,  showing  that  fer- 
mentation has  begun.  Add  a  little  yeast  to  another  bottleful,  and 
notice  that  fermentation  begins  within  a  few  hours.  Boil  another 
bottleful  and  at  once  cork  it  tightly,  and  notice  that  it  does  not  change. 
Explain  that  the  first  bottleful  started  with  few  germs  and  so  fermenta- 
tion at  first  was  slow.  The  second  had  many  and  fermentation  began 
at  once.  In  the  third  the  yeast  germs  were  destroyed  and  so  no  fer- 
mentation took  place. 

19.  Set  aside  a  bottle  of  weak  molasses  and  water  for  a  week  or  two. 
Notice  that  fermentation  goes  on  but  that  the  liquid  now  tastes  sour, 
for  it  has  become  vinegar. 

20.  Soak  a  yeast  cake  in  water  for  a  few  hours  and  examine  a  tiny 
drop  under  the  microscope  with  a  power  of  at  least  200  diameters. 
Notice  the  small  oval  cells,  from  the  edges  of  which  tiny  cells  seem  to 
be  budding.  These  are  yeast  cells.  In  the  same  specimen  starch 
grains  will  appear  as  much  larger  irregular  bodies  of  a  shape  depending 
upon  the  kind  of  grain  used  in  making  the  yeast. 

21.  Procure  some  alcohol.  Notice  its  sharp  odor  and  taste.  Show 
that  it  will  dissolve  and  remove  grease  from  the  hands.  Explain  that 
in  the  arts,  it  is  used  to  dissolve  oils,  resins,  and  such  substances  as 
water  will  not  dissolve.  Procure  some  wood  spirits  and  contrast  its 
odor  and  taste  with  that  of  common  alcohol.  Show  that  it,  too, 
dissolves  grease. 

22.  Pour  some  alcohol  upon  the  white  of  an  egg.  Notice  that  the 
alcohol  coagulates  it  and  turns  it  white. 

23.  Place  a  small  piece  of  tender  meat  in  a  bottle  of  alcohol  for 
a  day  or  two.  Notice  that  it  turns  whitish  in  color  and  becomes 
shriveled,  hard,  and  dry.  Explain  that  the  alcohol  takes  away  the 
coloring  matter  of  the  meat,  and  also  coagulates  the  albumin  much  in 
the  same  way  as  hemlock  bark  tans  leather.  Explain  how  alcohol  pre- 
serves substances  in  this  way. 

OV.   PHYSIOL.  —  4 


50  APPLIED   PHYSIOLOGY 

24.  Dip  a  small  piece  of  paper  in  alcohol  and  touch  it  with  a  match. 
It  bursts  into  a  flame  at  once,  and  develops  great  heat  but  no  smoke. 
Notice  that  the  paper  does  not  burn  until  the  alcohol  is  nearly  used  up. 
Explain  that  in  the  body  alcohol  seems  to  be  easily  oxidized,  and  uses 
oxygen  which  should  go  to  the  proper  food  of  the  body. 

25.  Hold  a  cold  stone  in  the  mouth  of  a  teakettle  or  in  the  steam  of 
a  pan  of  water.  Notice  that  the  vapor  condenses  in  drops  upon  the 
stone.  This  will  illustrate  distillation  as  well  as  a  comphcated  appa- 
ratus of  coils  and  running  water.  Explain  that  dew  upon  the  grass  is 
a  distillation  of  water. 

REVIEW  TOPICS 

1.  Describe    how    alcohol    and   vinegar    are    commonly 

formed. 

2.  Describe  \h^  yeast  plant. 

3.  Dtscriho,  another  of  vinegar. 

4.  T)ts>Q,r\bQ  fer7ne7itatio7i. 

5.  Tell  how  fermentation  is  applied  to  bread  making. 

6.  Describe  malt  liquoi's. 

7.  Describe  wi7ie. 

8.  Describe  spi7'its  and  the  process  by  which  they  are 

made. 

9.  Describe  alcohol. 

10.  Give  the  three  main  properties  and  effects  of  alcohol. 

11.  Tell  what  becomes  of    alcohol  when  taken   into   the 

body. 

12.  Tell  why  alcohol  does  not  satisfy  thirst. 


CHAPTER   V 
DIGESTION   OF  FOOD   IN   THE  MOUTH 

64.  Food  and  digestion.  —  Albumin,  fat,  and  sugar  are 
continually  being  oxidized  in  the  body,  and  the  products 
of  oxidation,  together  with  mineral  matter  and  water,  are 
being  thrown  off.  In  order  to  keep  up  the  strength  and 
form  of  the  body  a  constant  stream  of  new  material  must 
be  supplied. 

Anythmg  which,  taken  inside  of  the  body,  supplies  it  with 
weight,  heat,  or  energy  is  food  (see  pp.  64  and  89). 

In  preparation  for  the  use  of  the  body,  food  is  reduced  to  a  form  which 
can  be  dissolved  in  water,  and  drawn  through  the  walls  of  the  blood 
tubes.  The  blood  distributes  it  to  all  parts  of  the  body.  The  process 
of  producing  a  chemical  change  in  food  so  that  it  can  be  taken  up  by 
the  blood  is  digestion. 

Man  uses  as  food  a  combination  of  albumin,  fat,  sugar  or  starch, 
mineral  matters,  and  water,  which  are  identical  with  the  proximate  prin- 
ciples of  the  body.  Of  these  water  and  mineral  matters  can  enter  the 
blood  without  being  changed,  while  the  albumin,  fat,  sugar,  and  starch 
require  digestion.  Albumin  is  changed  to  a  form  called  peptone,  which 
can  easily  diffuse  through  the  walls  of  the  blood  tubes,  and  so  become 
a  part  of  the  blood. 

Sugar  and  starch  are  both  changed  to  glucose,  a  form  of  sugar  found 
in  the  grape.     Fat  is  saponified  and  emulsified. 

65.  Cooking.  —  Digestion  is  begun  by  applying  heat  to 
food,  either  with  or  without  water.  Preparing  food  by 
heat  is  cookiiig.  The  heat  of  cooking  coagulates  the 
albumin.     It   also    softens    and   dissolves   the    connective 

51 


52  APPLIED   PHYSIOLOGY 

tissue  which  binds  together  the  cells  of  the  food  material, 
and  thus  makes  meat  and  vegetables  tender.  It  devel- 
ops an  agreeable  flavor  which  stimulates  the  desire  for 
food  and  promotes  digestion.  Cooking  has  no  effect  upon 
fat  itself,  but  the  tiny  pockets  of  albumin  in  which  it  is 
stored  in  meat  and  vegetables  are  softened  or  dissolved 
away,  and  the  fat  is  set  free.  In  vegetables  and  flour, 
starch  is  in  tiny  grains,  each  of  which  seems  to  be 
made  up  of  layers  of  starch  separated  by  thin  layers  of 
a  waterproof  substance.  Hot  water  causes  the  starch  to 
swell  and  burst  these  envelopes,  and  the  starch  itself  is 
then  dissolved,  thickening  the  water  to  a  jellylike  mass. 
Cooking  has  no  effect  upon  the  sugar  and  mineral  matters 
of  the  food,  except  to  mingle  them  thoroughly  with  the  food. 
Thorough  cooking  also  destroys  many  poisons,  and  all 
the  disease  germs  in  tainted  food.  Yet  cooking  does  not 
render  tainted  food  fit  for  use. 

66.  Ways  of  cooking.  —  Some  foods  are  best  cooked  by  being 
boiled  or  stewed.  Other  foods  are  best  when  roasted  or  broiled.  The 
exact  method  is  not  so  important  as  the  skill  of  the  one  who  does  the 
cooking. 

In  all  forms  of  cooking  the  principles  are  the  same.  If  the  solid  food 
alone  is  to  be  eaten,  as  much  of  the  juices  as  possible  should  be  retained 
in  the  food  by  coagulating  the  albumin  upon  the  outside  at  once  so  as  to 
imprison  the  juices.  This  can  be  done  by  having  the  water  boil  before 
the  food  is  placed  in  the  kettle,  or  by  placing  the  food  in  a  hot  oven. 
The  film  which  forms  upon  the  outside  of  the  food  effectually  seals  the 
juices  within.  If  both  the  solid  food  and  the  liquid  in  which  it  is 
cooked  are  to  be  eaten,  the  flavors  are  better  developed  if  the  juices  are 
diffused  through  the  liquid.  In  this  case  the  food  should  be  placed  in 
cold  water  or  a  cool  oven,  and  heat  applied  gradually  so  as  to  avoid 
coagulating  the  exterior  sooner  than  the  interior.  In  most  cases  the 
food  will  be  of  better  quality  and  taste  if  the  cooking  is  done  slowly. 
When  the  heat  is  continued  after  the  food  is  thoroughly  softened,  its 
fibers  are  apt  to  become  hard  and  dry. 


DIGESTION   OF  FOOD   IN  THE  MOUTH 


53 


As  a  general  rule  it  is  best  to  cook  each  kind  of  food  separately. 
Each  substance  can  then  be  cooked  in  its  own  peculiar  manner.  In 
roasting  and  broiling,  the  fat  drips  away.  The  outside  of  the  meat, 
subjected  to  a  high  degree  of  heat,  becomes  hard,  imprisoning  the 
juices  within.  The  inner  part  of  the  meat  is  protected  from  the  heat 
and  is  cooked  at  a  lower  temperature 
than  the  outside.  So  its  juices  remain 
in  a  more  natural  state. 

When  food  made  from  vegetables  or 
grain  is  baked,  a  crust  forms  upon  the 
outside.    This  consists  of  hardened  albu-  *■'  /  . 

min  mixed  with  starch,  which  is  partly  ' 

changed  by  the  heat  to  a  kind  of  sugar. 
If  the  crust  is  not  too  much  cooked  and 
dried  it  is  palatable  and  easily  digested. 

67.  The  alimentary  canal. — 
Food  is  taken  into  the  body  and 
digested  by  means  of  a  tube  lead- 
ing through  the  body.  Beginning 
at  the  upper  end,  the  parts  of  this 
tube,  which  is  called  the  alimen- 
tary canal,  are  the  mouth,  phar- 
ynx, esophagus,  stomach,  and 
intestine. 

68.  The  mouth. — The  food  is 
held  in  the  mouth  for  a  few  sec- 
onds while  it  is  mixed  with  the 
watery  fluid  called  the  saliva,  and 
ground  fine  by  the  teeth.  This 
grinding  is  mastication,  and  the  mixture  with  saliva  is  in- 
salivation.  In  these  two  processes,  the  teeth,  tongue, 
cheeks,  lips,  and  salivary  organs  all  take  part.  The 
roof  of  the  mouth  is  formed  by  the  bony  palate  in  front, 
and  the  soft  movable  palate  behind.  It  is  bounded  on 
the    sides   and   in   front  by  the   teeth,  cheeks,    and    lips. 


The  alimentary  canal. 


54 


APPLIED    PHYSIOLOGY 


The    floor    is    formed    by    the    tongue    and    the    lower 
jaw. 

69.  The  jaws. — The  lower  jaw  is  a  semicircular  bone, 
whose  hinder  extremities  are  curved  upwards.  Each  tip 
forms  a  hinge  which  turns  in  a  socket  just  in  front  of  the 
ear.  It  carries  a  semicircle  of  teetJi,  which  exactly  fit 
against  a  similar  semicircle  upon  the  upper  jaw.  The 
lower  jaw  is  moved  by  powerful  muscles  in  three  direc- 
tions :  first,  up  and  down  ;  second,  sidewise ;  third,  back- 
ward and  forward. 

The  upper  jaw  is  a  strong  bone  of  irregular  shape,  firmly 
fixed  to  the  rest  of  the  skull.  Its  interior  is  hollowed  out 
to  form  a  cavity  called  the  antrum^  which  has  a  small 
opening  into  the  nose.  The  upper  ends  of  the  teeth  some- 
times project  so  far  upward  as  to  make  slight  elevations 
upon  its  floor.     Sometimes  an  inflammation  or  abscess  of 

a  tooth  may  extend  to  the 
antrum,  so  that  it  becomes 
filled  with  pus,  producing  a 
very  serious  trouble. 

70.  Teeth.  —  The  teeth  are 
hard,  bony  pegs  set  deeply 
into  the  lower  jawbone  and  in 
the  edge  of  the  hard  palate. 
There  are  sixteen  on  each 
jaw.  Counting  from  the  mid- 
dle of  the  front  of  each  jaw,  the 
first  two  on  each  side  are  like 
chisels,  so  as  to  bite  or  gnaw 
off  the  food,  and  are  called  the 
incisors.  In  a  squirrel,  they 
are  long  and  sharp,  so  as  to  gnaw  through  wood.  The 
third  tooth  is  the  canine.     It  is  a  round,  firmly  set  tooth, 


The  teeth  at  the  age  of  six  and 
one  half  years.  /,  tlie  incisors ; 
O,  the  canine;  M,  the  molars;  the 
last  molar  is  the  first  of  the  permanent 
teeth ;  F,  sacs  of  the  permanent  in- 
cisors; C,  of  the  canine;  /?,  of  the 
bicuspids;  N,  of  the  second  molar; 
the  sac  of  the  third  molar  is  empty.  — 
Marshall. 


DIGESTION   OF  FOOD   IN  THE   MOUTH 


55 


which  in  animals  is  the  tusk.  The  next  two  are  larger, 
with  flat  surfaces  ;  they  are  called  bicicspids.  The  next 
three,  the  gjHnders,  or  molars,  have  large,  flat  surfaces, 
well  adapted  to  grinding  the  food. 


In  a  young  child  the  two  bicuspid  teeth  resemble  the  molar  teeth  in 
the  adult,  and  the  three  molars  are  absent.  At  about  the  age  of  six,  a 
whole  new  set  of  teeth  begins  to  grow  beneath  the  first  teeth,  and  to 
press  against  their  roots,  cutting  off  their  food  supply.  The  blood 
takes  away  the  substance  of  the  old  teeth  as  the  new  ones  advance 
against  them,  until  their  projecting  parts  alone  are  left  attached  only  by 
the  gum.  They  finally  drop  out.  while  the  new  ones 
advance  to  take  their  places.  The  first  teeth,  like 
the  permanent  set,  may  decay  and  cause  toothache, 
and  should  have  as  good  care  in  filling  and  cleaning 
as  is  given  to  permanent  teeth. 

Sometimes  when   a   baby's   gums   are    being   cut 
through  by  the  growing  first  teeth,  they  are  tender 
and  swollen,  making  the  child  fretfiil 
seldom  causes  sickness  in  a  healthv  child. 


Yet  teething 


Section  of  a  tooth. 

a  enamel. 

b   dentine. 

c  pulp  cavity  con- 
taining blood 
tubes  and 
ner\^es. 

d  cement. 


71.  Composition  of  teeth.  —  The  teeth 
are  composed  of  a  very  hard  kind  of  bone 
called  dentine,  which  in  some  large  animals 
is  called  ivory.  It  is  nourished  by  blood 
tubes   and   nerves,   which  enter  at  the   tip 

within  the  jaw  and  form  a  pulplike  mass  in  a  small  cavity 
in  the  center  of  each  tooth.  The  root  of  the  tooth  is  set 
into  a  socket  in  the  jawbone,  and  a  kind  of  soft  bone, 
called  the  ceinent,  fixes  it  in  place.  The  projecting  part  of 
each  tooth,  called  the  crown,  is  covered  wdth  a  hard  shell 
called  the  e7ianiel. 

72.  Care  of  teeth.  —  When  the  enamel  is  too  thin,  or  is  worn  or 
broken  off,  the  dentine  beneath  it  may  decay.  Then  the  tooth  rapidly 
goes  to  pieces,  often  with  much  pain.  Picking  the  teeth  with  pins  and 
cracking  nuts  often  break  the  enamel.  Dirt  and  particles  of  food  be- 
tween the  teeth  are  great  promoters  of  decay.     The  saliva  deposits  a 


56 


APPLIED   PHYSIOLOGY 


brown  substance  called  tartar^  which  may  press  the  gum  back  from  the 
root  of  the  tooth,  until  a  part  of  the  tooth  below  the  enamel  is  reached. 
Then  the  tooth  may  decay  and  break  off  at  the  gum,  or  the  gum  and 
bone  may  be  forced  back  from  the  crown  until  the  tooth  becomes  loose 
and  drops  out.  Thoroughly  brushing  the  teeth  twice  a  day  with  a 
tooth  brush  and  water  is  necessary  for  preserving  the  teeth.     Particles 


9/     'J    /J"  ,• 


The  tongue. 

of  food  between  the  teeth  should  be  removed,  either  by  a  soft  wooden 
toothpick  or  else  by  passing  a  strong  thread  between  the  teeth.  Still, 
with  the  best  of  care,  some  decayed  cavities  may  develop,  and  these 
should  be  filled  at  once.  With  this  care,  almost  any  set  of  teeth  should 
last  a  lifetime. 

The  cheeks  and  lips  are  thin  layers  of  skin  and  muscles, 
which  can  be  moved  freely  in  all  directions. 


DIGESTION   OF  FOOD   IN  THE  MOUTH 


57 


The  tongue  is  a  long,  flat  muscle,  attached  at  its  back 
end  only,  while  its  front  part  is  capable  of  varied  and  pre- 
cise movements  in  every  direction. 

73.  Mucous  membrane.  —  The  cavity  of  the  mouth  is 
everywhere  lined  with  a  thin  membrane,  directly  continu- 
ous with  the  outside  skin.  It  consists  of  a  loose  network 
of  cells  carrying  blood  tubes  and  nerves.  It  is  covered 
with  a  layer  of  flat  cells,  called  epithelmni.  Into  the  loose 
tissue  beneath  the  epithelium,  there  project  pockets  or 
tubes  lined  with  cells  directly  continuous  with  the  epi- 
thelial cells  of  the  sur- 
face of  the  mouth.  In 
health,  the  cells  of  each 
of  the  tubes  and  of  the 
surface  of  the  mouth  pro- 
duce just  enough  of  a 
thin,  clear  liquid,  called 
mucus ^  to  moisten  and 
lubricate  the  surface  of 
the  mouth.  This  mem- 
brane is  called  a  mucous 
fiieinbraue .  It  is  continued  into  the  stomach  and  intestine, 
and  into  the  windpipe  and  lungs. 

Mucous  membrane  is  modified  skin  turned  in  from  the  surface  of  the 
body  to  line  the  interior  of  all  the  cavities  which  communicate  directly 
with  the  air.  Every  such  surface  is  covered  by  an  unbroken  laver  of 
epithelial  cells.  Wherever  the  epithelial  cells  are  absent,  the  spot  is 
raw  and  sore.  The  epithelial  cells  of  the  surface  of  the  mucous  mem- 
brane are  designed  mainly  for  protection  :  but  those  which  reach  into 
the  tubes  are  set  apart  for  the  special  work  of  producing  mucus  from 
material  supplied  by  the  blood. 


0\e 


Mucous  membrane  (X  200). 

a  cells  and  loosely  woven  fibers  forming  the 

main  part  of  the  membrane. 
b  mucous  glands  cut  across. 
c  epithelium  upon  the  surface. 


74.    Gland   and   secretion.  —  A  collection  of  pockets  or 
tubes  lined  with  epithelium  which  forms  a  substance  out 


58 


APPLIED    PHYSIOLOGY 


of  the  blood  is  a  gland.  The  substance  formed  is  called  a 
secretion.  The  epithelium  of  the  gland  does  all  the  work 
of  secreting.  All  the  mucous  membranes  of  the  body  con- 
tain glands  which  secrete 
^  a  mucus,  and  in  addition 
many  contain  glands 
which  secrete  other  sub- 
stances. 

75.  Sore  mouth.  — 
Babies  sometimes  suffer 
with  a  form  of  sore  mouth 
in  which  white  specks,  like 
curdled  milk,  appear  upon 
its  mucous  membrane. 
The  spots  are  due  to  a 
kind  of  mold  which 
grows  in  milk.  Gently 
washing  the  mouth  with 
clean,  warm  water  several 
times  a  day  will  destroy 
the  mold  and  remove 
the  sores. 

76.  Salivary  glands.  — 
The  mouth  contains  a 
fluid,  called  saliva,  which 
enters  it  from  three  tubes 
on  each  side.     Each  sali- 


Diagram  of  glands. 

a  epithelium  upon  the  surface  of  a  mucous 

membrane. 
b   the   epithelium  continued   into   a   simple 

tube. 
c   the   epithelium  continued   into   a   simple 


pocket. 
d  the  epithelium  continued  into  a  series  of     vary  tubc,  after  it  haS  CX- 

branching  tubes  and  pockets.  tended  iuto  the  flcsh  on 

b,  c,  and  d  are  glands. 

the  face  for  an  inch  or 
so,  abruptly  divides  again  and  again  like  the  branches 
and  twigs  of  a  tree.  At  the  end  of  the  smallest  divi- 
sions,   there    are    minute    pouches    ^-J-q    of    an    inch    in 


DIGESTION   OF  FOOD   IN  THE  MOUTH 


59 


diameier.  All  these  tubes  and  pouches  are  rolled  into 
a  small  mass  with  blood  tubes  and  nerves.  The  whole 
collection  is  called  a  salivary  gland.  Each  tube  and 
pouch  is  lined  with  epitheHal  cells  which  make  the  saliva 
out  of  the  fluid  parts  of  the  blood  in  which  they  are 
always  bathed.  The  saliva  flows  out  of  the  tubes  into 
the  mouth  as  fast 
as  it  is  secreted. 
There  is  a  sali- 
vary gland  in 
front  of  each  ear, 
called  the  pajvtid 
gland ;  one  along 
each  side  of  the 
lower  jaw,  called 
the  submaxillary 
gland,  and  one 
just  under  each 
side  of  the  front 
end  of  the  tongue, 
called  the  sub- 
liiigiial  gland. 

77.  Saliva.  — 
The  saliva  is  a 
thin,      colorless, 


r\ 


oiZia^^fl^^ 


f>'', 


vr 


The  salivary  glands. 


alkaline  mixture,  which  often  contains  air  bubbles.  About 
YoVo  P^^^  ^^  ^^^  saliva  is  a  white  substance  called  ptyalin, 
which  has  the  power  to  change  starch  to  glucose  while 
remaining  unchanged  itself.  Hence,  ptyalin  is  a  ferment. 
It  can  act  only  in  an  alkaline  fluid,  and  its  action  stops  when 
the  food  is  acted  on  by  the  stomach.  It  digests  only  a 
small  amount  of  starch,  and  its  value  is  due  mainly  to  the 
water  it  contains. 


6o 


APPLIED    PHYSIOLOGY 


78.  Use  of  the  water  in  saliva. — The  water  of  the  saliva  has 
very  important  uses.  The  nerves  of  taste  are  covered  by  the  epithelium 
of  the  mucous  membrane,  and  some  of  the  food  must  be  carried  through 
this  epithelium  to  the  nerves  in  order  that  it  may  be  tasted.  The  water 
of  the  saliva  dissolves  the  food  and  soaks  through  the  epithelium^ 
carrying  a  tiny  amount  of  food  to  the  nerves,  and  thus  makes  the  sense 
of  taste  possible. 

During  digestion,  food  must  be  reduced  to  a  fluid  condition  as  thin 
as  milk.     The  saliva  begins  the  process.     Enough  saliva  is  mixed  with 

food  to  form  a  pasty  mass  which  the 
thin  walled  stomach  can  handle  with 
ease. 


79.    Production     of     saliva.  — 

Saliva  enters  the  mouth  continu- 
ally, but  between  meals  only 
about  an  ounce  an  hour  is  pro- 
duced, while  during  a  meal  the 
food  increases  in  weight  about 
one  half  by  the  addition  of  saliva. 
From  one  to  three  pints  are  pro- 
duced daily.  The  flow  of  saliva 
is  excited  by  the  act  of  chew- 
ing, and  by  anything  held  in 
the  mouth,  especially  if  it  be  of  an  agreeable  taste  and 
odor.  Hunger,  or  the  sight  or  thought  of  agreeable  food, 
"makes  the  mouth  water."  The  longer  food  is  chewed 
the  more  saliva  is  produced.  This  mixing  and  dissolving 
action  of  the  saliva  is  greatly  aided  by  the  movements  of 
the  various  parts  of  the  mouth. 

80.  Mastication.  —  A  morsel  of  food  is  pushed  between  the 
molar  teeth,  which  crush  and  grind  it  by  the  three  movements  of  the 
lower  jaw.  Between  each  movement  of  the  jaw,  the  tongue  and  cheeks 
roll  the  morsel  into  a  firm  mass  so  that  the  teeth  can  act  upon  it  to 
better  advantage.  The  tongue  has  a  delicate  sensibility  for  the  proper 
condition  and  position  of  the  food,  and  its  varied  and  precise  move- 


A  salivary  gland  ( X  200) . 

a  tube  of  epithelium  forming  the 
gland,  cut  lengthwise. 

b    tubes  cut  crosswise. 

c  connective  tissue  binding  the 
tubes  in  place. 


DIGESTION   OF   FOOD    IN  THE   MOUTH 


6i 


ments,  aided  by  the  movements  of  the  lips  and  cheeks,  keep  the  food 
in  the  best  position  for  the  action  of  the  teeth.  In  a  few  seconds,  even 
hard  and  dry  food  becomes  a  thin  and  pasty  mass.  The  tongue  col- 
lects the  mass  into  a  ball  in  the  back  part  of  the  mouth  in  preparation 
for  its  passage  to  the  stomach.  The  process  of  sending  food  from  the 
mouth  to  the  stomach  is  sival- 
lowiiig  or  deghititio7i . 

81.    The      pharynx.  — 

Back  of  the  tongue  is  a 
muscular  bag  about  four 
and  a  half  inches  in 
length,  lying  against  the 
spinal  column  and  called 
the  phary7ix.  It  is  lined 
with  mucous  membrane, 
which  secretes  far  more 
mucus  than  that  of  the 
mouth.  When  the  secre- 
tion of  mucus  is  excessive 
it  is  called  catarrJi,  but  it 
is  usually  a  harmless 
affection.  The  pharynx 
has  seven  openings ;  one 
into  the  esophagus  or 
muscular  tube  leading  to 
the  stomach ;  one  into 
the  beginning  of  the 
windpipe ;  one  into  the  mouth ;  two  into  the  nose,  and  two 
into  the  middle  ear.  The  openings  to  the  nose  and  ears 
can  be  closed  by  raising  the  soft  palate  against  the  spinal 
column.  The  windpipe  can  be  closed  in  three  ways : 
first,  by  the  root  of  the  tongue  arching  itself  backward 
over  the  windpipe ;  second,  by  a  cover  to  the  windpipe, 
called    the    epiglottis ;    third,    by  the    vocal  coi'ds   sliding 


Diagram  of  the  beginning  of  swallowing. 

a   top  of  tongue. 

b   pharynx. 

c    morsel  of  food. 

d  sliding  door  of  the  front  of  the  pharynx. 

e    soft  palate. 

f  epiglottis. 


62 


APPLIED    PHYSIOLOGY 


together  in  the  middle.  The  opening  to  the  mouth  can 
be  closed  by  two  upright  muscles  which  hang  between  the 
back  part  of  the  soft  palate  and  the  base  of  the  tongue. 

These  two  muscles  come 
together  in  the  middle 
like  sliding  doors. 

82.  Swallowing.  —  By 
a  conscious  effort,  the 
tongue  quickly  pushes  the 
morsel  of  food  backward 
towards  the  pharynx.  The 
two  upright  muscles  of 
the  pharynx,  gliding  to- 
gether over  the  surface  of 
■f  the  tongue  between  it  and 
the  food,  cut  the  food  off 
from  the  mouth.  During 
this  movement  the  phar- 
ynx  closes    all   its   other 

Diagram  of  second  part  of  swallowing.  .  ,    ,  i 

^  openings,  except  the  one 

a   top  of  tongue  arched   backward   and  up- 

ward.  to  the  csophagus.      The 

b  pharynx.  ioQ,^   is  uow  bcyond   the 

c    morsel  of  food  pushed  into  the  pharynx  by  ^^ 

the  back  of  the  tongue.  COntrol  of  the   will.       The 

d  sliding  doors  of  the  pharynx  which   have  ^USCleS    of     the     pharynx 
come  together  m  the  middle.  ^  •' 

e   soft  pal  ate  lifted  up  ward  to  shut  off  the  nose.  itSclf     nOW     Contract,    for- 

/  epiglottis   folded    downward    to   close   the  ^  ^y^^     ^^^^     -^^^^     ^j^^ 

larynx.  c? 

esophagus,    the    opening 
of  which  is  the  only  one  not  closed. 

83.  The  esophagus. — The  esophagus  is  a  muscular 
tube  connecting  the  pharynx  with  the  stomach.  It  is 
about  nine  inches  in  length.  It  is  lined  with  mucous 
membrane  and  secretes  only  enough  mucus  to  moisten  its 
surface.     When  food  reaches  it,  a  ring  of  the  muscular 


DIGESTION   OF   FOOD   IN  THE   MOUTH  63 

tube  contracts  just  above  the  morsel.  This  contraction 
runs  down  to  the  stomach,  forcing  the  food  before  it  as 
though  a  tight  iron  ring  were  slipped  down  over  the  esopha- 
gus. A  contraction  of  a  tube  within  the  body  in  a  regular 
manner,  producing  an  onward  movement  of  its  contents, 
is  called  peristalsis.  While  a  horse  is  drinking,  the  peri- 
stalsis of  the  esophagus  may  be  plainly  seen  along  its 
neck. 

SUMMARY 

1.  Anything  which  taken  inside  the  body  supplies  it  with 

weight  or  heat  or  energy  is  food. 

2.  All  foods  are  composed  of  one  or  more  of  the  five  sub- 

stances :  water,  albumin,  fat,  starch  or  sugar,  and 
mineral  matter. 

3.  Food  must  become  liquid  in  form  and  enter  the  blood 

tubes  before  it  can  reach  the  cells  of  the  body. 

4.  Cooking  softens  the  food  and  develops  its  flavors.     It 

also  destroys  many  poisons  in  food. 

5.  In  the  mouth  food  is  ground  fine  between  the  teeth 

and  mixed  with  the  saliva  so  as  to  form  a  thin  paste. 

6.  Saliva  contains  a  ferment  which  changes  some  of  the 

starch  of  the  food  to  sugar. 

7.  The  tongue  pushes  the  chewed  food  backward  into 

the  pharynx.  The  pharynx  then  closes  all  its 
openings  except  the  one  into  the  esophagus.  The 
pharynx  then  squeezes  the  food  into  the  esophagus, 
and  the  esophagus  forces  it  into  the  stomach. 

8.  All  cavities  of  the  body  which  have  an  opening  leading 

to  the  air  are  lined  with  a  kind  of  soft  skin  called 
mucous  membrane. 

9.  Mucous   membrane  is  a  network  of   cells   and   fibers 

covered  with  flat  cells  called  epitheliitm. 


64  APPLIED   PHYSIOLOGY 

10.  Mucous  membranes  contain  little  pockets  of  epithelial 

cells,  which  produce  a  slippery  fluid  called  mucus. 

11.  A  collection  of  pockets  or  tubes,  lined  with  epithelium, 

which  separates  a  substance  from  the  blood,  is  a 
gland. 

12.  The  saliva  is  formed  in  three  glands  upon  each  side 

of  the  face. 

DEMONSTRATIONS 

26.  Notice  the  various  movements  of  the  teeth  and  tongue,  lips  and 
cheeks,  in  chewing.  Have  one  of  the  pupils  open  his  mouth  wide. 
Show  how  the  soft  palate  which  forms  the  roof  of  the  mouth  can  be 
raised  and  lowered.  Show  the  sliding  doors  of  the  pharynx,  which 
reach  up  to  the  soft  palate  and  with  it  form  an  arch  over  the  back  part 
of  the  tongue.  Notice  the  small  projection  which  points  downwards 
from  the  summit  of  the  arch.     This  is  called  the  uvula. 

2j.  Have  the  pupils  swallow  slowly.  Notice  that  the  tongue,  begin- 
ning at  the  tip,  is  applied  to  the  roof  of  the  mouth  until  its  whole  length 
touches  the  palate.  Notice  that  when  the  back  part  of  the  throat  begins 
to  swallow,  the  food  is  beyond  the  control  of  the  will.  Notice  that 
breathing  is  stopped,  for  both  the  nose  and  windpipe  are  closed. 

28.  Get  a  tooth  and  have  it  sawed  in  two  lengthwise,  so  as  to  show 
the  cavity  in  its  interior.  Get  another,  partly  decayed,  to  show  how  the 
nerves  of  the  interior  are  laid  bare  and  exposed  to  injury. 

29.  Procure  the  lower  jaw  of  a  sheep  or  pig.  With  a  hammer  and 
chisel  split  open  a  part  of  the  bone  to  show  how  the  teeth  are  set  into 
the  bone. 

30.  Point  out  the  difference  between  the  skin  and  the  mucous  mem- 
brane of  the  lips.  Notice  that  the  two  are  directly  continuous.  Explain 
that  the  mucous  membrane  is  really  a  modified  skin,  and  that  anything 
in  the  mouth  and  stomach  is  really  outside  the  body  proper  just  as  it 
would  be  if  it  were  held  in  the  closed  hand. 

31.  Examine  a  specimen  of  mucous  membrane  under  the  micro- 
scope, using  a  power  of  at  least  200  diameters.  Notice  the  layer 
of  epithelial  scales  covering  its  outside.  Notice  the  network  of  fine 
connective  tissue  which  makes  up  the  main  part  of  the  membrane. 
Notice  the  glands.    They  are  tubes,  but  are  cut  across  in  the  specimen. 


DIGESTION   OF   FOOD   IN  THE   MOUTH  65 

and  appear  as  circles  lined  with  large  cells.     Explain  that  the  cells 
of  the  glands  produce  the  mucus. 

32.  Have  a  boy  open  his  mouth  and  raise  his  tongue  upward  and 
backward.  With  a  handkerchief  wipe  dry  the  space  between  the  tongue 
and  teeth.  In  a  moment  a  drop  of  water  will  collect  between  the  small 
projections  near  the  tongue.  Move  the  tongue  slightly,  and  notice 
that  the  liquid  flows  m  a  tiny  stream.  Explain  that  this  is  the  saliva 
flowing  from  the  sublingual  gland. 

33.  Chew  a  piece  of  white  bread.  After  a  little,  notice  that  it  has  a 
sweetish  taste.  Explain  that  the  sweetness  is  due  to  the  action  of  the 
ptyalin  of  the  saliva  in  changing  the  starch  to  sugar. 

34.  While  a  horse  or  a  cow  is  drinking,  notice  the  peristalsis  of  the 
esophagus  along  its  neck  as  it  swallows  each  mouthful. 


REVIEW  TOPICS 

1.  Define  food  and  name  the  five  classes. 

2.  Tell  what  change  each  must  undergo  in  order  to  enter 

the  body. 

3.  Tell  what  effect  cooking  has  upon  each  class  of  food. 

4.  Discuss  the  different  ways  of  cooking. 

5.  Give  the  parts  of  the  alimentary  canal. 

6.  Describe  the  month. 

7.  Describe  Xho^jaws  and  teeth. 

8.  Tell  how  the  teeth  are  commonly  injured,  and  how  to 

preserve  them. 

9.  Describe  the  cheeks,  lips,  and  tongue. 

10.  Describe  a  viucons  nionbrmie. 

1 1 .  Define  a  gland. 

12.  Describe  a  salivary  gland. 

13.  Describe  the  use  and  appearance  of  saliva. 

14.  Describe  mastication. 

15.  Describe  thQ  pharynx. 

16.  Describe  swallowing. 

1 7.  Describe  peristalsis. 

OV.  PHYSIOL.  —  5 


CHAPTER   VI 


STOMACH  DIGESTION 


84.    Cavities  of  the  body.  —  A  muscular  partition,  curved 
sharply  upward,  divides  the  inside  of  the  body  into  two 

cavities,  —  an  upper  one, 
called  the  chest  or  tJiorax^ 
which  contains  the  hem^t, 
lungs,  and  the  esophagus, 
and  a  lower  one,  called 
the  abdomen,  which  con- 
tains the  st07nach,  intes- 
ti7te,  liver,  spleen,  and 
g  kidneys.  This  muscular 
1  partition  is  called  the 
diapJwagm. 

85.  The  abdomen  and 
peritoneum.  —  The  abdo- 
men is  a  closed  cavity, 
bounded  above  by  the 
diaphragm,  on  the  sides 
partly  by  the  ribs,  and 
behind  partly  by  the 
spinal  column.  The  bones 
of  the  pelvis  form  its  floor. 
The  rest  of  its  walls  are 
formed  by  thick  sheets  of 
muscles.  It  is  lined  with  a  very  smooth  membrane  called 
the  perito7ienm. 

66 


Organs  of  the  chest  and  abdomen. 

a  larynx. 

b  trachea. 

c  clavicle,  or  collar  bone. 

d  sternum,  or  breastbone. 

e  lung. 

/  heart. 

g  liver. 

h  stomach. 

i  large  intestine. 

/  small  intestine. 


STOMACH    DIGESTION 


67 


The  peritoneum  also  covers  the  outside  of  all  the  abdominal  organs. 
Such  a  membrane,  lining  a  cavity  which  is  not  in  open  communication 
with  the  air,  is  a  serous  membrane.  The  peritoneum  is  the  largest  and 
most  important  serous  membrane.  It  is  a  thin,  closely-woven  network 
of  interlacing  cells  covered  by  a  single  layer  of  flat  cells,  which  give  it 
a  shiny  appearance.  It  is  moistened  by  a  small  quantity  of  watery  fluid, 
which  is  not  produced  by  glands,  but  is  a  part  of  the  lymphatic  circu- 
lation.     Its    smoothness    per- 

o 

mits  easy   movements   among 
the  organs  of  the  abdomen. 


86.  The  stomach.— The 

stomach  is  the  first  organ  /■ 
into  which  the  food  passes 
when  it  leaves  the  esoph- 
agus. It  lies  mostly  on  the 
left  side  of  the  abdomen 
half  covered  by  the  lower 
ribs.  It  is  a  conical  en- 
largement of  the  alimen- 
tary canal,  and  is  situated 
between  the  esophagus 
and   the  small   intestine. 


Organs  in  the  upper  part  of  the  abdomen. 

a  liver,  raised  up. 

b  gall  bladder  upon  the  under  surface  of  the 
liver. 

c    spleen. 

d  stomach. 

e  pancreas  ;  the  line  passes  through  the  com- 
mon opening  of  its  tube  and  that  from 
the  gall  bladder. 


It  is  about  twelve  inches  ^  duodenum. 
in  length  and  five  inches 

in  diameter.  It  is  composed  of  a  layer  of  muscle  covered 
with  peritoneum  and  lined  with  mucous  membrane.  Its 
walls  are  from  -^^  to  \  inch  in  thickness.  It  is  hung  in 
place  by  a  short  curtain  of  peritoneum,  which  is  attached 
above  to  the  under-surface  of  the  liver  and  diaphragm. 
The  esophagus  opens  into  the  stomach  at  its  upper  left 
side,  called  the  cardiac  extremity.  The  opening  into  the 
intestine  is  at  the  right  and  narrowest  part,  and  is  called 
the  pylorus.  The  pylorus  can  be  closed  by  a  thick  ring  of 
muscle. 


68 


APPLIED    PHYSIOLOGY 


87.  Glands  of  the  stomach.  —  The  mucous  membrane  of 
the  stomach  contains  numerous  glands  which  secrete  a 
special  digestive  fluid  called  the  gastric  juice.  The  glands 
are  short  tubes  each  about  2^0"  ^^  ^^  vii&i  in  diameter, 
and  -^-^  of  an  inch  in  length.  The  tubes  are  set  closely 
together  and  resemble  pinpricks  in  the  mucous  mem- 
brane. Each  tube  is  lined  with 
a  single  layer  of  epithelial  cells 
which  produce  the  gastric  juice 
from  material  supplied  by  the 
blood.  Besides  these  glands 
there  are  many  others  which 
secrete  only  mucus. 

88.  Gastric  juice.  —  The  gas- 
tric juice  is  a  yellov/ish  fluid, 
and  consists  of  water  holding 
in  solution  hydrochloric  acid 
and  two  ferments.  These  are 
the  essential  agents  in  stomach 
digestion.  Hydrochloric  acid  is 
produced  by  the  epithelium  of 
the  gastric  tubes  from  the  salt 
contained    in    the    blood,    and 


Gastric   glands  in  the  stomach 
(X  200). 


a  epithelium  of  the  surface  of  the 

stomach. 
b  epithelium  lining  the  tubes  of  the 

glands. 
c  connective    tissue    between     the 

tubes. 


forms  from  -j;^-^ 


to   5^0  of  the 


gastric  juice.  The  ferments 
are  white,  albuminous  substances  produced  from  the  blood 
by  the  epithelium  of  the  glands,  and  form  about  -5-J-Q  of 
the  gastric  juice.  The  flow  of  gastric  juice  is  promoted 
by  a  slow,  steady  in-taking  of  food  at  about  the  tempera- 
ture of  the  body.  The  saliva,  which  is  slightly  alkaline, 
an  agreeable  taste  of  the  food,  and  a  pleasant  frame  of 
mind  also  aid  its  flow.  About  three  quarts  enter  the 
stomach  each  day. 


STOMACH   DIGESTION  69 

89.  Peristalsis  of  the  stomach.  —  Anything  taken  into 
the  stomach  causes  a  continuous  and  regular  movement 
of  the  organ,  due  to  the  alternate  contraction  and  relax- 
ation of  its  muscular  fibers.  This  is  an  example  of  slow 
peristalsis.  The  food  is  thus  caused  to  flow  in  a  steady 
stream  from  the  esophagus  to  the  left,  and  then  down  to 
the  right  and  back  again,  completing  the  circuit  of  the 
stomach  in  about  three  minutes.  By  this  movement  it  is 
thoroughly  mixed  with  the  gastric  juice. 

90.  Ferments  of  the  gastric  juice.  —  One  of  the  ferments 
of  the  gastric  juice,  rennhi^  acts  by  coagulating  milk.  In 
the  child  this  action  is  very  important. 

The  other  ferment,  pepsin^  softens  the  albumin  of  food 
and  changes  its  character  so  that  it  will  dissolve  in  water 
and  diffuse  through  the  walls  of  the  blood  tubes  to  become 
a  part  of  the  blood.     This  form  of  albumin  is  called /^/^;2^. 

A  quarter  of  a  grain  of  pepsin  can  render  a  whole  white  of  an  ^gg 
soluble.  It  acts  best  at  the  temperature  of  the  bod}-,  and  there  must 
be  an  acid  present.  The  surface  of  the  food  particles  are  acted  upon 
first,  and  the  products  of  its  action  are  rubbed  off  by  the  peristalsis  of 
the  stomach,  and  the  next  layer  is  acted  upon  in  the  same  manner. 
Some  of  the  gastric  juice  penetrates  between  the  particles  of  food,  and 
slowly  eats  its  way  into  the  food  mass,  thus  dissolving  apart  the  sepa- 
rate cells  which  compose  the  food.  Its  action  is  confined  solely  to  the 
albumin.  In  fat  meat  the  albuminous  pockets  are  eaten  away,  and  the 
fat  is  set  free.  Starch  is  not  acted  upon,  except  to  be  freed  from  its 
albuminous  envelopes. 

The  result  of  stomach  digestion  is  a  fluid  called  cJiyvte. 
Peptone  imparts  to  it  a  bitter  taste,  while  small  particles 
of  fat  give  it  a  milky  appearance.  Food  then  appears  as 
it  would  if  it  had  been  boiled  for  a  long  time. 

91.  Use  of  the  acid.  —  Pepsin  can  act  only  in  the  presence  of 
the  acid,  in  an  amount  at  least  sufficient  to  neutralize  the  alkali  always 


70  APPLIED   PHYSIOLOGY 

present  in  the  food.     The  gastric  juice  is  more  often  deficient  in  acid 
than  in  pepsin. 

Besides  assisting  the  pepsin  the  acid  alone  can  perform  the  first 
stages  of  changing  albumin  to  peptone.  Living  germs  of  fermentation 
and  disease  are  sometimes  swallowed.  The  acid  destroys  them  if  it  is 
present  in  the  gastric  juice  in  its  full  amount.  This  is  a  provision  of 
nature  to  prevent  fermentation  from  taking  place  in  the  stomach,  which 
might  otherwise  become  sour  at  every  meal.  This  explains  why 
diseases  are  more  easily  caught  w^hen  the  stomach  is  deranged.  In 
a  healthy  person  the  germs  meet  the  destroying  acid  almost  at  the 
entrance  to  the  body. 

92.  Amount  of  stomach  digestion.  —  The  stomach  digests 
only  albumin.  The  main  uses  of  the  stomach  are,  to  act 
as  a  storehouse  for  food,  to  mix  it  with  the  watery  gastric 
juice,  and  to  reduce  it  to  a  form  still  more  Hquid  than 
when  it  left  the  mouth.  The  acid  prevents  the  food  from 
spoiHng,  and,  with  the  pepsin,  begins  the  digestion  of  the 
albumin.  The  stomach  is  not  absolutely  necessary  for 
digestion,  but  because  of  its  capacity  it  enables  us  to  carry 
a  store  of  food  so  that  we  do  not  need  to  eat  every  few 
minutes. 

93.  Passage  of  food  into  the  intestine.  —  Every  minute 
or  two  the  pylorus  opens,  permitting  a  little  of  the  chyme 
to  escape  into  the  intestine,  where  the  main  work  of  diges- 
tion is  performed. 

Some  food  begins  to  pass  out  of  the  stomach  within  a 
few  moments  after  eating.  The  time  required  for  the 
stomach  to  empty  itself  completely  is  from  two  to  five 
hours,  depending  upon  the  amount  of  food  and  the  ease 
with  which  it  is  broken  up.  Thus  we  commonly  say  that 
it  takes  from  two  to  five  hours  for  food  to  digest. 

When  the  stomach  has  been  empty  for  some  time,  there 
is  a  sense  of  hunger.  Yet  the  intestine  may  still  contain 
enough  undigested  food  to  supply  the  body  for  hours. 


STOMACH   DIGESTION  7 1 

SUMMARY 

1.  The  diaphragm  divides  the  inside  of  the  body  into  an 

upper  cavity  called  the  thorax  and  a  lower  one  called 
the  abdomen. 

2.  In  the  abdomen  are  the  organs  of  digestion. 

3.  The  lining  of   the   abdomen   and  the  covering   of  its 

organs  is  a  smooth  membrane  called  peritoneum. 

4.  The  stomach  is    a   muscular  bag   lined  with    mucous 

membrane  and  covered  with  peritoneum.  In  its 
mucous  membrane  are  glands  which  produce  the 
gastric  juice. 

5.  The  gastric  juice  is  water  containing  hydrochloj-ic  acid, 

and  two  ferments.     It  changes  albumin  to  peptone. 

6.  The  actions  of  the  stomach  may  be  summed  up  in  three 

things:  (i)  It  is  a  storehouse  in  which  food  is  held 
while  being  passed  on  to  the  intestine  in  a  slow  and 
steady  stream.  (2)  Its  peristaltic  movements  break 
up  the  food  and  mix  it  with  the  gastric  juice.  (3)  It 
digests  some  albumin  by  means  of  the  acid  and 
pepsin  of  the  gastric  juice. 

7.  Every  minute  or  two  some  of  the  liquefied  food  passes 

through  the  pylorus  into  the  intestine. 

8.  In  from  two  to  five  hours  after  a  full  meal  the  stomach 

is  usually  empty. 

9.  The   stomach   has  no   action   upon   starch  or  fat,  and 

digests  only  a  part  of  the  albumin. 

DEMONSTRATIONS 

35.  Show  the  internal  organs  of  an  animal.  A  frog  or  a  mouse  will 
do ;  but  a  rat.  a  rabbit,  or  a  cat  will  be  better. 

Always  prepare  the  specimen  in  private,  and  leave  it  before  the  class 
only  while  it  is  actually  being  shown.  Cover  all  the  parts  except  those 
to  be  shown,  and  wash  away  all  traces  of  blood.    Any  small  animal  may 


72  APPLIED    PHYSIOLOGY 

be  killed  quickly  and  painlessly  by  placing  it  in  a  tight  box  or  covered 
pail  and  pouring  in  half  an  ounce  of  chloroform.  Demonstrations  of 
the  internal  organs  had  better  be  made  only  before  those  members 
of  classes  who  wish  to  see  them. 

36.  It  is  well  to  preserve  permanent  specimens  of  the  different 
organs.  One  part  of  formalin  to  30  parts  of  water  is  most  excellent. 
It  is  neither  expensive  nor  poisonous,  while  it  preserves  specimens  in 
their  natural  form  and  color.  The  following  inexpensive  mixture, 
known  as  M'uller's  fluids  is  also  good. 

Sodium  sulphate  (Glauber's  salt),        i  part, 
Potassium  bichromate,  2  parts, 

Water,  100  parts. 

This  forms  a  yellow  fluid  and  stains  the  specimens  yellow.  It  is 
only  slightly  poisonous,  even  if  taken  into  the  mouth,  while  soap  and 
water  will  remove  it  from  the  hands. 

Put  the  specimen  in  a  large  covered  earthen  or  glass  jar,  with  an 
amount  of  the  fluid  equal  to  at  least  five  times  the  bulk  of  the  speci- 
men. Remove  it  from  the  jar  to  a  platter  when  showing  it  to  the 
class.  The  fluid  will  harden  the  tissues  so  that  even  soft  organs  may 
be  handled  with  safety. 

Special  training  is  required  in  preparing  microscopic  specimens 
showing  the  tissues  in  their  proper  position.  The  difficulty  consists  in 
cutting  a  slice  thin  enough  ;  for  the  microscope  magnifies  in  thickness 
as  well  as  in  length  and  breadth. 

37.  Open  the  abdomen  of  a  dead  animal  by  a  cut  from  the  ribs  to 
the  end  of  the  body.  Notice  that  the  organs  and  walls  of  the  abdomen 
are  shiny  from  their  covering  of  peritoneum.  Notice  that  the  perito- 
neum is  thin  and  strong,  that  its  appearance  differs  from  that  of  a 
mucous  membrane,  and  that  it  can  be  peeled  from  the  abdominal 
walls.     (See  demonstration  35.) 

38.  Notice  the  shape  and  position  of  the  stomach.  Open  it  to  show 
the  folds  in  the  mucous  membrane.  With  a  specimen  of  mucous  mem- 
brane under  the  microscope  show  the  short,  straight  gastric  glands  stand- 
ing side  by  side.     Sketch  them.     (See  demonstration  35.) 

39.  Notice  the  dome  of  muscle  extending  completely  across  the  body 
above  the  stomach.  Explain  that  this  is  the  diaphragm,  and  that  it 
divides  the  body  into  two  cavities.  Open  the  chest  and  show  its  cavity 
and  the  top  of  the  diaphragm,  which  separates  it  from  the  abdominal 
cavity.     (See  demonstration  35.) 


STOMACH    DIGESTION  73 

40.  Illustrate  stomach  action  by  placing  small  slices  of  hard-boiled 

^gg  in  — 

Hydrochloric  acid,         40  drops, 

Pepsin,  I  grain, 

Water,  i  pint. 

Keep  the  mixture  in  a  warm  place,  shaking  it  occasionally.  In  a  few 
days  the  egg  will  completely  dissolve.  Show  some  powdered  pepsin 
and  some  dilute  hydrochloric  acid. 

41.  Boil  some  potatoes  and  meat  for  several  hours,  to  illustrate  the 
appearance  of  chyme  as  it  leaves  the  stomach . 

REVIEW  TOPICS 

1.  Describe  the  two  raain  cavities  of  the  body. 

2.  Describe  the  lijting  of  tJie  abdomen. 

3.  Describe  a  serous  membrane. 

4.  Describe  the  sto^nach. 

5.  Describe  \^^  gastric  juice  and  the  glands  in  which  it 

is  formed. 

6.  Tell  the  name  and  the  action  of  the  acid  of  the  gastric 

juice. 

7.  Tell  the  names  and  the  actions  of  the  two  ferments. 

8.  Tell  how  each  class  of  food  is  affected  by  the  stomach, 

and  how  much. 

9.  Describe  the  peristaltic  movements  of  the  stomach. 

10.  Tell  how  the  food  passes  from  the  stomach  into  the 

intestine. 

11.  Tell  how  important  the  work   of  the   stomach  is  in 

comparison  with  the  work  done  in  the  intestine. 


CHAPTER   VII 

ABNORMAL  ACTION  OF  THE   STOMACH 

94.  The  appetite.  —  Eating  is  designed  to  furnish  the 
body  with  proper  nourishment,  but  many  "  Uve  to  eat," 
and  pay  for  their  meals  with  a  host  of  bad  feehngs.  The 
amount  and  kind  of  food,  and  the  time  of  eating,  must  be 
suited  to  the  needs  of  the  body.  A  wild  animal  eats  and 
thrives  without  thought  of  what  it  eats,  for  nature  has 
given  it  certain  signs  which  it  follows  blindly  and  yet 
securely.  Man  possesses  the  same  signs,  and  if  they 
were  followed,  indigestion  would  be  rare.  The  sign  of 
the  need  of  food  is  the  feeling  of  hunger  and  thirst,  or  the 
appetite.  The  kind  of  food  required  is  indicated  by  the 
sense  of  taste,  and  the  proper  amount  of  food  is  known  by 
the  absence  of  hunger  and  by  the  sense  of  taste  begin- 
ning to  fail. 

95.  Natural  taste  of  food.  —  The  simplest  kind  of  food 
tastes  the  best  to  a  hungry  person.  He  eats  it  with  keen 
enjoyment  until  his  hunger  is  satisfied.  If  he  leaves  the 
table  now  and  goes  about  his  work,  his  meal  will  digest 
without  producing  unpleasant  feelings. 

Food  flavored  only  with  salt  has  a  natural  taste  of  which 
we  never  tire,  and  which  gives  reliable  signs  as  to  the 
quantity  needed,  and  the  time  of  eating.  If  only  this 
kind  of  food  is  placed  upon  the  table,  the  sense  of  taste 
and  the  satisfied  feeling  at  the  end  of  the  meal  are  reli- 
able guides  as  to  the  amount  and  kind  of  food  needed. 

74 


ABNORMAL  ACTION   OF  THE   STOMACH  75 

96.  Perverted  appetite.  —  After  hunger  has  been  satisfied  with 
all  the  food  needed,  a  food  with  an  artificial  taste  is  often  brought  on, 
and  a  new  appetite  arises.  The  taste  soon  learns  to  prefer  the  arti- 
ficially prepared  food,  and  the  education  of  "living  to  eat"  is  begun. 
Pie,  cake,  sweets  of  all  kinds,  spices,  and  seasonings  are  eaten  mainly 
to  please  an  acquired  appetite. 

Sweets  and  highly  seasoned  food  do  not  satisfy  a  hungry  man  as 
plain  food  does,  but  on  the  contrary  their  taste  becomes  sickening  to 
the  stomach,  before  they  begin  to  satisfy  his  hunger.  Moreover,  the 
appetite  for  artificial  things  may  persist  after  the  stomach  is  filled. 

97.  Intemperate  eating.  —  In  the  hurry  of  business  or  pleasure 
men  gulp  down  their  dinners  in  huge  mouthfuls,  and  overload  their 
stomachs  before  the  surprised  organs  can  take  account  of  the  kind  or 
quantity  of  food  eaten.  Some  eat  too  much  in  prolonging  the  pleas- 
ures of  taste.  Nearly  everybody  indulges  an  appetite  for  sweets  and 
highly  seasoned  food.  Satisfying  an  appetite  which  is  not  the  expression 
of  actual  need  of  the  body  is  as  much  intemperance  as  drinking  strong 
drink,  and  leads  to  the  same  kind  of  serious  results. 

98.  Insufficient  mastication.  —  A  whole  train  of  evils  follows 
intemperate  eating.  When  food  is  swallowed  in  large  lumps  instead 
of  being  masticated  to  a  thin  gruel,  too  little  saliva  is  mixed  with  it.  It 
reaches  the  stomach  too  dry,  and  so  a  larger  amount  of  gastric  juice  is 
needed.  But  the  saliva  is  the  natural  stimulant  to  the  flow  of  juice, 
and  if  it  is  small  in  amount,  the  gastric  juice  does  not  flow  in  sufficient 
quantity  and  food  is  not  well  digested. 

99.  Too  much  food.  —  An  excessive  amount  of  food  stretches 
and  weakens  the  stomach,  and  peristalsis  cannot  take  place  so  vigorously 
as  it  should.  The  lumps  of  food  are  neither  penetrated  by  the  gastric 
juice  nor  ground  to  pieces  by  the  peristalsis,  but  only  their  outer  sur- 
faces are  slowly  dissolved.  The  food  thus  remains  too  long  a  time 
in  the  stomach,  and  some  may  stay  there  until  the  next  meal. 

100.  Eating  between  meals.  —  Eating  at  irregular  hours  or 
between  meals  also  disturbs  the  stomach.  Two  or  three  hours  after  a 
meal  the  work  of  the  stomach  should  be  done,  and  it  should  be  per- 
mitted to  rest.  If  more  food  of  any  kind  is  eaten,  the  stomach  must 
either  be  overworked  or  the  food  not  be  digested. 

Food  which  the  gastric  juice  softens  with  difficulty  behaves  like 
large  lumps  of  food,  and  finally  either  is  vomited,  or  is  passed  on  to  the 
intestine  to  create  more  trouble  there. 


76  APPLIED   PHYSIOLOGY 

101.  Fermentation  in  the  stomach.  —  The  stomach  cannot  be 
abused  in  any  way  without  suffering  in  all  its  actions.  It  gives  expres- 
sion to  its  suffering  by  pain,  headache,  heart  beating,  and  a  host  of  other 
bad  feelings.  It  makes  the  whole  body  weak  and  sick.  Its  imperfect 
action  also  permits  fermentation  to  go  on,  which  makes  the  food  sour. 
Living  germs  like  those  producing  alcohol  and  vinegar  are  continually 
being  eaten.  In  health,  the  acid  of  the  gastric  juice  destroys  them, 
but  when  anything  weakens  the  acid  or  prevents  it  from  reaching  the 
germs,  they  grow  and  produce  vinegar  and  other  acids,  and  also  gases. 
The  result  is  a  sour  stomach  and  '•  wind  on  the  stomach,"  which  comes 
up  and  out  of  the  mouth  as  though  it  were  vomited.  This  is  a  sign 
of  indigestion. 

The  gas  distends  the  stomach  and  presses  it  against  the  heart,  so  that 
the  beats  are  felt ;  and  then  the  heart  and  not  the  stomach  receives  the 
blame.  A  sour  stomach  is  at  first  the  result  of  improper  action,  not  the 
cause ;  but,  once  developed,  it  may  cause  a  greater  disturbance,  and 
then  there  is  only  a  step  to  actual  stomach  disease. 

102.  Drinking  while  eating.  —  A  great  part  of  the  work 
of  digestion  consists  in  mixing  food  with  water.  When 
dry  food  is  eaten,  the  gastric  juice  must  be  produced  in 
large  amount  before  digestion  can  begin.  A  glass  or  two 
of  water,  either  alone  or  with  tea  or  coffee,  aids  the  action 
of  the  gastric  juice.  If  the  water  is  not  used  in  place  of 
saliva  in  moistening  the  food,  or  is  not  employed  to  hasten 
the  act  of  swallowing  food,  drinking  during  meals  will  be 
beneficial.     Many  drink  too  Httle  liquid. 

103.  Hot  or  cold  food.  —  Food  either  too  hot  or  too  cold 
hinders  the  production  and  action  of  the  gastric  juice  and 
disturbs  peristalsis,  so  that  the  movements  of  the  stomach 
may  not  resume  their  natural  course  until  a  long  time  after 
the  temperature  of  the  food  becomes  that  of  the  body. 
A  glass  of  ice  water  may  remain  perceptibly  cold  to  the 
stomach  for  from  one  quarter  to  half  an  hour,  and  its 
effects  upon  the  movements  of  digestion  may  last  much 
longer. 


ABNORMAL  ACIION   OF  THE   STOMACH  77 

104.  Rest  and  eating,  —  When  the  body  is  very  tired, 
the  stomach  has  not  the  proper  energy  for  digesting  food. 
If  food  is  eaten  just  as  a  person  comes  home  fatigued  by 
a  hard  day's  work,  there  is  apt  to  be  a  night  of  pain  and 
indigestion.  If,  before  eating,  a  glass  of  warm  water  or 
coffee  or  milk  is  taken,  followed  by  a  short  nap,  so  as  to 
rest  the  body,  the  meal  will  be  enjoyed,  and  digestion  will 
go  on  unaccompanied  by  bad  feelings. 

After  a  meal  the  stomach  requires  an  extra  amount  of 
blood  and  energy.  A  rest  of  fifteen  minutes  after  each 
meal  would  be  a  great  health  saver. 

105.  Rules  for  eating.  —  Chew  each  mouthful  to  a  paste 
and  swallow  it  before  taking  another. 

Stop  as  soon  as  the  taste  of  plain  food  begins  to  pall. 
Allow  four  or  five  hours  to  elapse  before  eating  again. 

SUMMARY 

1.  Hunger  indicates  the  need  of  food,  and  taste  indicates 

the  kind. 

2.  When  only  plain  food  is  eaten,  these  two  signs  are  cor- 

rect guides  in  eating. 

3.  An  appetite  for  sweet  and  highly  seasoned  food  may  per- 

sist after  hunger  has  been  satisfied  with  plain  food. 

4.  Sweet  and  seasoned  foods  soon  disgust  the   sense   of 

taste,  thus  showing  that  they  are  not  needed. 

5.  Eating  food  for  mere  pleasure  is  i7itcmperance. 

6.  Eating  too  much,  too   rapidly,   or  too  often  is   intem- 

perance. 

7.  As  a  result  of  intemperate   eating,  acid   fermentation 

often  occurs  in  the  stomach,  producing  discomfort 
and  sickness. 

8.  A   person   should  eat  only  plain  food,  slowly,  and  at 

intervals  of  not  less  than  four  or  five  hours. 


yS  APPLIED   PHYSIOLOGY 

DEMONSTRATION 

42.  Nearly  every  one  has  felt  the  effects  of  intemperate  eating. 
When  "  stomach  sick/''  a  sharp-tasting  gas  and  very  sour  food  often 
come  up  to  the  mouth,  showing  that  acid  fermentation  is  going  on. 
Notice  how  plainly  a  person  feels  his  own  heart  beats  after  a  large  meal, 
owing  to  the  pressure  of  the  distended  stomach  upon  the  heart. 

REVIEW  TOPICS 

Tell  how  a  person  knows  when  and  how  much  to  eat 
or  drink. 

Define  an  appetite  and  tell  how  it  can  be  satisfied 
naturally. 

Illustrate  an  artificial  appetite  and  tell  how  it  can  be 
distinguished  from  a  natural  appetite. 
4.    Tell  some  of  the  ways  in  which  men  abuse  their  stom- 
achs by  indulging  their  artificial  appetites. 

Tell  some  of  the  effects  of  too  rapid  eating ;  of  imper- 
fect mastication ;  of  overeating ;  of  eating  between 
meals. 

6.  Tell  how  food  sours  within  the  stomach. 

7.  Tell  how  drinking  at  meal  times  is  beneficial,  and  in 

what  way  it  can  be  harmful. 

8.  Tell  how  hot  or  cold  food  affects  the  stomach. 

9.  Give  some  simple  rules  for  eating. 


CHAPTER   VIII 


mXESTINAL  DIGESTION 


106.  The  intestine. — The  part  of  the  alimentary  canal 
below  the  stomach  is  called  the  intestme.  The  intestine  is 
a  tube  of  varying  size, 
whose  different  parts 
have  different  names. 
Next  to  the  stomach 
is  the  small  intestine, 
which  is  about  one 
inch  in  diameter  and 
about  twenty  feet  in 
length.  It  opens  into 
the  large  intestine, 
which  is  about  two 
inches  in  diameter  and 
five  feet  in  length. 

107.  The  small  in- 
testine. —  The  small 
intestine  is  very  movable,  and  is  coiled  in  the  abdomen  in 
no  definite  order.  It  is  held  in  place  by  a  fanlike  fold  of 
peritoneum,  called  the  mesentery.  The  mesentery  is  about 
four  inches  in  length  along  its  back  edge,  which  is  fastened 
to  the  spinal  column,  and  twenty  feet  at  its  outer  edge,  to 
which  the  intestine  is  attached.  Its  breadth  from  the  spinal 
column  to  the  intestine  is  about  four  inches. 

79 


Diagram  representing  a  cross  section  of  the 
small  intestine,  showing  the  three  layers,  and 
the  way  in  which  the  blood  tubes  pass  be- 
tween the  two  folds  of  serous  membrane  (the 
peritoneum)  which  forms  the  mesentery. 


8o 


APPLIED   PHYSIOLOGY 


In  front  of  the  intestine,  and  partly  enwrapping  its  folds,  is  a  thin 
apron  of  peritoneum,  called  the  ojnentuui.  It  contains  much  fat,  and 
acts  as  a  cushion  and  as  protection  against  cold.  The  small  intestine 
for  about  ten  inches  from  the  stomach  is  called  the  duodemun.  Then 
for  about  eight  feet  it  is  called  the  jejunum^  and  the  remaining  eleven 
feet  is  called  the  ileum.  There  is  no  very  marked  difference  between 
any  two  sections  of  these  divisions. 

The  intestine  ends  at  about  the  level  of  the  hip  bone, 
and  opens  into  the  side  of  the  large  intestine  by  a  slitlike 
valve,  which  permits  matter  to  pass  into  the  large  intes- 
tine, but  to  a  great  extent  prevents  its  backward  movement. 

108.  The  large   intestine,  or  colon.  —  The  whole  large 

intestine  is  called  the 
colon.  Its  beginning 
is  a  small  pouch  called 
the  ccBcitniy  which  is 
situated  on  the  right 
side  of  the  abdomen 
at  the  level  of  the  hip 
bone. 

From  the  caecum 
there  extends  a  small  tube  one  quarter  of  an  inch  in 
diameter  and  two  inches  long,  closed  at  its  outer  end. 
This  tube  is  called  the  vermiform  appe^tdix.  It  sometimes 
becomes  inflamed,  forming  an  abscess,  and  produces  the 
disease  called  appendicitis. 

The  colon  extends  upward  to  the  ribs,  then  crosses  the 
abdomen  to  the  left  side,  and  then  extends  downward. 
These  parts  are  called  the  ascending,  t^-ansverse,  and  de- 
scendijig  colon.  The  colon  is  held  in  place  by  a  narrow 
fold  of  peritoneum.  It  is  not  an  even  tube,  but  looks  as 
though  strings  were  tied  about  it  at  intervals  of  a  few  inches. 

109.  Structure  of  the  intestine. — The  whole  intestine 
consists    of    a  tube   of   muscular  tissue,   whose  walls   are 


A  piece  of  intestine  showing  the  folds  of  the 
valvulae  conniventes  upon  its  inner  surface. 


INTESTINAL   DIGESTION  8 1 

from  iV  to  i  of  an  inch  in  thickness.  It  is  covered  with 
peritoneum  and  lined  with  mucous  membrane.  Its  muscle 
fibers  extend  both  lengthwise  and  circularly.  In  the  mucous 
membrane  of  the  small  intestine  are  folds,  eacn  of  which 


Villi  (X  200). 
a   epithelium  upon  the  surface  of  the  villi. 

b   connective  tissue  fibers  which  support  the  blood  tubes  and  lacteals. 
c    connective  tissue  cells. 
d  glands  which  form  the  intestinal  juice. 
e    intestinal  gland  cut  across. 

extends  from  one  half  to  three  fourths  the  way  around  the 
intestine.  The  folds  are  called  valvtilce  conniventes.  Upon 
the  surface  of  each  fold  are  fino:erlike  projections  called 
villi,  which  are  from  ^  to  ^  of  an  inch  in  length,  and 
from  2io'  t^  TO  0^  ^^  '^^^  ^^  diameter.  Between  the  bases 
of  the  vilU  minute  tubes,  2^0  ^^  ^^  '^^^^  ^^  length  and  -^ 

OV.  PHYSIOL.  —  6 


82 


APPLIED    PHYSIOLOGY 


of  an  inch  in  diameter,  extend  into  the  mucous  membrane. 
Each  tube  is  Uned  with  a  layer  of  epitheHal  cells,  which 
secrete  a  fluid  called  the  intestinal  jince. 

110.    Villi.  —  Each  villus  consists  of  an  outer  covering 

of  epithelial  cells,  inclos- 
ing a  loose  meshwork  of 
fine  blood  tubes,  and  also 
of  tubes  called  lacteals^ 
both  of  which  take  up 
the  food  as  it  is  di- 
gested. Neither  villi  nor 
valvulae  conniventes  are 
found  in  the  large  intes- 
tine. 

111.  The  pancreas.  — 
From  the  duodenum  there 
extends  a  very  short  tube, 
about  the  size  of  a  small 
quill.  This  divides  into 
two  tubes,  one  of  which 
goes  to  the  liver  and  the 
other  to  the  pancreas. 
The  pancreas  is  a  gland 
about  an  inch  in  diameter 
and  six  inches  long,  lying 
behind  the  stomach.  In 
lower  animals  it  is  called  the  sweetbread.  Its  structure 
resembles  that  of  a  salivary  gland.  It  secretes  a  thin, 
watery  liquid  called  the  pancreatic  juice,  which  is  poured 
into  the  intestine  at  the  rate  of  one  and  a  half  pints  a 
day. 

112.    The  liver.  —  The  liver  is  a  firm,  dark-red,  wedge- 
shaped  organ,  lying  under  the  lowest  ribs  upon  the  right 


Diagram  of  the  essential  parts  of  a  villus. 

a   epithelium  which  takes  up  food  and  trans- 
ports it  to  the  tubes  within. 
b   an  artery.        c    capillaries.        d  a  lacteal. 


INTESTINAL  DIGESTION 


83 


side.     It  is  covered  with  peritoneum  and  hung  closely  to 
the  diaphragm  and  the  spinal  column. 

The  tube  leading  from  the  intestine  to  the  liver  divides 
again  and  again  into  branches  called  bile  ducts,  the  small- 


A  thin  slice  of  liver  (x  200). 

a  veins  bringing  blood  to  the  liver.  c  liver  cells. 

b  capillaries  between  the  liver  cells.  d  vein  to  carry  blood  away  from  the  liver. 

e  tubes  to  carry  away  bile. 

est  of  which  are  exceedingly  minute,  and  barely  recog- 
nizable with  a  microscope.  The  walls  of  the  smallest  of 
these  ducts  are  composed  of  large  cells  of  irregular  shape, 
which  crowd  one  another  so  that  the  bile  tubes  are  almost 
closed.  These  cells  make  up  the  greater  part  of  the  liver. 
Among  these  tubes  there  run  many  fine  blood  tubes,  in 
such  a  manner  that  the  cells  seem  to  be  arranged  around 


84  APPLIED   PHYSIOLOGY 

the  capillaries  instead  of  around  the  bile  tubes.  Each  cell 
makes  bile  from  the  blood  and  pours  it  into  its  bile  tube, 
down  which  it  runs,  uniting  with  streams  from  other  tubes. 
All  the  tubes  finally  unite  their  streams  in  the  single  bile 
tube  which  leads  to  the  intestine.  A  side  tube  leads  from 
the  large  bile  tube  to  a  bladder  on  the  under  side  of  the 
liver,  called  the  gall  bladder,  which  stores  the  bile  when  it 
is  not  needed  in  the  intestine. 

113.  Bile.  —  Bile  is  a  thick,  golden-colored  liquid  of  a 
very  bitter  taste.  It  consists  of  waste  albuminous  matter, 
coloring  substances,  and  mineral  matters  dissolved  in  water. 
Although  it  is  a  waste  product,  it  has  very  important  uses 
in  digestion.     About  a  quart  is  produced  daily. 

114.  Intestinal  fluids.  —  As  the  food  enters  the  intestine 
it  finds  three  new  substances  ready  to  act  upon  it.  These 
substances  are  the  ijitestinal  j?ncc,  Xh^  pancreatic  juice,  and 
the  bile.  All  these  liquids  are  alkaline,  and  tend  to  neu- 
tralize the  acid  in  the  food  as  fast  as  it  comes  from  the 
stomach. 

115.  Intestinal  juice. — The  intestinal  juice  is  small  in 
amount,  and  contains  ferments  which  change  starch  to 
glucose,  and  albumin  to  peptone ;  but  its  action  is  slight, 
and  the  amount  digested  by  it  is  small. 

116.  Pancreatic  juice.  —  The  pancreatic  juice  is  a  liquid 
of  which  five  per  cent  is  made  of  three  ferments  which 
perform  the  main  part  of  digestion.  As  the  chyme  comes 
from  the  stomach,  it  contains  albumin,  some  already  di- 
gested, but  much  only  softened  and  broken  up.  It  also 
contains  fat  and  starch  unchanged. 

One  of  the  ferments  of  the  pancreatic  juice,  tiypsin, 
acts  upon  the  undigested  albumin,  changing  it  to  pep- 
tone. 

Another   ferment,  amylopsin,   changes   the    starch    and 


INTESTINAL   DIGESTION  85 

sugar   to    glucose.     It   does    practically  all   the  work   of 
digesting  starch  and  sugar. 

The  third  ferment,  steapsin,  saponifies  some  of  the  fat 
with  the  soda  and  potash  of  the  chyme.     About  one  half 
an  ounce  of  soap  is  thus  formed  daily.     It  acts  as  a  lubri- 
cating and  cleansing  agent.     The  ferment  also  emulsifies' 
the  remainder  of  the  fat. 

117.  Action  of  the  bile.  —  About  a  quart  of  bile  is  poured 
into  the  intestine  each  day.  It  has  a  slight  power  in  emul- 
sifying fat,  and  in  converting  starch  into  glucose,  but  while 
its  direct  action  is  small,  it  does  a  great  amount  of  work  in 
helping  and  stimulating  all  the  processes  in  the  intestine. 
It  almost  doubles  the  power  of  the  pancreatic  juice.  It 
acts  as  a  lubricant  to  enable  the  food  to  slip  down  the 
intestine  easily.  It  stimulates  the  peristalsis  of  the  intes- 
tine, and  prevents  the  growth  of  germs  of  fermentation. 
It  also  enables  digested  food  to  pass  more  readily  from 
the  intestine  into  the  blood  tubes.  When  bile  is  of  poor 
quality,  or  too  little  in  quantity,  digestion  is  less  perfectly 
performed,  and  headaches,  mental  dullness,  and  all  the 
symptoms  called  biliousness  result. 

118.  Peristalsis.  —  The  intestine  shows  peristaltic  move- 
ments like  those  in  the  esophagus.  A  half  an  inch  or  so 
of  muscle  fiber,  running  lengthwise  of  the  intestine,  con- 
tracts, pulling  the  next  lower  part  of  the  intestine  up  over 
a  lump  of  food.  Then  the  circular  fibers  contract,  squeez- 
ing the  food  down  the  tube,  while  the  fibers  next  below 
repeat  the  process,  as  the  first  ring  of  contraction  relaxes. 
So  the  contraction  runs  down  the  tube,  forcing  the  intestinal 
contents  before  it. 

This  peristalsis  is  a  slow,  gentle  movement.  By  it  the  intestinal 
contents  are  mixed  with  its  juices,  and  slowly  propelled  toward  the 
large  intestine,  where  it  is  propelled  still  more  slowly. 


86  APPLIED   PHYSIOLOGY 

119.  Result  of  intestinal  digestion.  —  By  the  action  of 
the  three  digestive  fluids,  the  food  is  dissolved  and  reduced 
to  a  thin,  milky  form,  called  chyle.  As  all  food  contains 
many  substances  wholly  indigestible,  some  solid  particles 
will  still  remain  in  the  chyle.  Digestive  action  goes  on 
during  the  whole  time  that  food  remains  in  the  intes- 
tine, but  most  of  the  work  is  done  in  the  small  intestine. 
As  it  slowly  passes  down  the  tube,  the  liquid  parts  are 
taken  up  until,  when  it  reaches  the  large  intestine,  it  has 
become  semi-solid  again.  The  expulsion  of  the  solid 
waste  which  finally  remains  is  the  last  act  of  digestion. 
It  takes  about  twelve  hours  for  food  to  pass  the  length  of 
the  small  intestine,  and  thirty-six  hours  to  traverse  the 
large  intestine. 

120.  What  becomes  of  the  ferments.  —  After  the  ferments  of 

the  gastric,  pancreatic,  and  intestinal  juices  have  done  their  work  of 
digestion,  they  are  probably  digested  by  the  new  ferments  poured  out 
at  the  next  meal,  for  they  are  albumin.  Bile  is  a  waste  product,  yet 
some  of  its  parts  are  taken  up  by  the  blood  and  carried  to  the  liver,  and 
again  poured  into  the  intestine.  Thus  nature  is  as  economical  as 
possible  with  the  resources  of  the  body. 

121.  Perfection  of  the  digestive  organs.  —  The  mouth  is 
perfectly  adapted  to  masticating  just  such  food  as  the 
stomach  can  readily  digest,  while  it  cannot  grind  such 
food  as  corn  or  hay.  The  stomach  seems  a  weak,  flabby 
organ,  but  nature  made  it  of  just  the  right  size  and  strength 
to  do  its  own  proper  work. 

The  bile  is  a  waste  product  of  the  body  and  yet  it  is 
one  of  the  most  important  agents  in  digestion.  In  brief, 
each  part  of  the  digestive  system  is  perfectly  adapted  to 
its  own  work.  In  lower  animals  the  digestive  organs  are 
somewhat  modified  so  as  to  adapt  them  to  different  foods 
and  different  modes  of  eating. 


INTESTINAL   DIGESTION  8/ 


SUMMARY 

1.  From  the  stomach  the  food  passes  into  a  long,  coiled 

tube  called  the  intestine. 

2.  In  the  intestine  the  food  is  acted  upon  by  ferments  in 

three  fluids  :  the  intestinal  juice,  \\i^ pancreatic  juice, 
and  the  bile. 

3.  The  intestinal   juice   has   a  slight  action   in   changing 

starch  to  sugar,  and  albumin  to  peptone. 

4.  The  pancreatic  juice  does  the  main  part  in  changing 

starch  to  sugar  and  albumin  to  peptone,  and  of 
emulsifying  and  saponifying  fats. 

5.  The  bile  greatly  increases  the  power  of  the  pancreatic 

juice.  It  also  lubricates  the  intestine,  prevents  fer- 
mentation, and  aids  the  passage  of  digested  food 
into  the  blood  tubes. 

6.  The    muscles   of   the   intestine    slowly  force  the  food 

down  the  tube  so  that  it  takes  about  twelve  hours 
for  food  to  traverse  the  small  intestine,  and  thirty-six 
to  traverse  the  large  intestine. 

DEMONSTRATIONS 

43.  Open  the  abdomen  of  a  dead  animal.  Notice  the  thin,  gauze- 
like omentum  containing  lumps  of  fat,  and  enveloping  the  intestine. 
Lift  it  up,  and  notice  that  the  upper  part  of  the  large  intestine  seems  to 
be  inserted  through  it  as  though  it  were  split  into  two  leaves.  Notice 
the  difference  between  the  small  and  large  intestine  in  position,  shape, 
and  movability.  Notice  the  beginning  of  the  large  intestine  and  the 
caecum.  The  vermiform  appendix  can  usually  be  found  also.  Notice 
the  position,  size,  and  feeling  of  the  liver,  and  the  gall  bladder  beneath 
it.  By  careful  search  the  pancreas  can  be  found  behind  the  stomach, 
lying  crosswise  of  the  body,  flattened  out  upon  the  backbone.  It  is 
covered  with  peritoneum  and  fat,  and  so  is  obscured,  but  can  be  recog- 
nized by  its  nodular  appearance.  A  pig's  sweetbread  has  much  the 
same  appearance  as  a  man's  pancreas.      (See  demonstration  35.) 


S8  APPLIED   PHYSIOLOGY 

Notice  the  thin  fanlike  mesentery,  holding  the  coil  of  intestine  in 
place.  Notice  the  blood  tubes  running  across  it.  Open  the  intestine 
for  a  few  inches  to  show  the  folds  of  the  valvulse  conniventes. 

44.  The  villi  are  too  soft  and  too  small  to  be  seen  without  a  specially 
prepared  specimen.     A  magnifying  power  of  50  will  show  them. 

Examine  also  a  specimen  of  the  liver,  using  at  first  a  power  of  100 
diameters.  Notice  the  capillaries  converging  toward  central  veins. 
The  bile  ducts  are  too  fine  to  be  seen. 

Next  use  a  power  of  400  diameters,  and  examine  the  cells  carefully. 
Notice  their  large  size,  and  that  they  sometimes  have  more  than  one 
nucleus.     Make  a  sketch  of  a  villus  and  of  the  liver  cells. 

45.  Pour  some  oil  into  a  bottle  of  water.  Shake  well,  and  notice 
that  the  two  cannot  be  made  to  mix.  Now  add  a  small  pinch  oi pancrea- 
iifie.  Shake  once  more,  and  notice  that  the  oil  now  forms  an  emulsion 
with  the  water. 

Explain  that  the  pancreatine  contains  the  ferment  of  the  pancreatic 
juice,  and  that  it  has  the  same  action  outside  the  body  that  it  does 
inside. 

46.  Make  a  little  starch  paste.  While  it  is  warm  stir  in  a  small 
pinch  of  pancreatine.  In  a  few  minutes  the  paste  becomes  fluid  from 
the  conversion  of  starch  to  sugar. 

47.  Procure  some  bile.  That  from  a  chicken's  gall  bladder  will  do. 
Pour  some  into  a  bottle  with  oil  and  water,  and  notice  that  it  forms  an 
emulsion. 

REVIEW  TOPICS 

1.  Describe  the   intestine  and  its  various  divisions  —  the 

small  and  the  large  intestine,  the  caecum,  the  vermi- 
form appendix,  the  colon,  the  mesentery,  and  the 
omentum. 

2.  Describe  the  pancreas. 

3.  Describe  the  liver. 

4.  Describe  the  bile  and  its  uses. 

5.  Describe  the  pancreatic  juice  and  its  three  ferments, 

and  their  uses. 

6.  Describe  the  intestinal  juice  and  its  use. 

7.  Describe  the  peristalsis  of  the  intestine. 


CHAPTER   IX 

> 

ABSORPTION  AND   ASSIMILATION 

122.  Absorption  of  food.  —  Digested  foods  which  be- 
come part  of  the  body  are  peptone,  glucose,  and  emulsified 
fat.  While  they  remain  in  the  intestine,  they  are  still 
outside  of  the  body  proper.  In  order  to  nourish  the  body, 
they  must  dialyze  through  the  wall  of  the  intestine  and 
become  part  of  the  blood.  The  process  of  taking  any  sub- 
stance into  the  blood  is  absorption. 

The  bodies  of  most  cells  are  semi-fluid  and  jellylike. 
The  peptone  and  glucose,  dissolved  in  water,  will  soak  into 
the  soft  epithelial  cells  lining  the  intestine,  while  the 
original  albumin  and  starch  or  sugar  will  not.  Blood  tubes 
run  so  near  the  inner  surface  of  the  wall  of  the  intestine, 
that  only  a  layer  of  epithelium  and  the  capillary  wall, 
both  together  thinner  than  the  thinnest  paper,  separate 
the  blood  from  the  food  in  the  intestine.  The  food  soaks 
through  the  epithelial  cells  and  the  walls  of  the  blood  tube, 
and  is  washed  away  by  the  blood  stream.  So  there  is  a 
steady  flow  of  digested  food  through  the  epithelial  cells 
toward  the  blood  tube  ;  while  the  undigested  food  remains 
behind.  The  cells  are  alive,  however,  and  to  a  degree 
select  what  they  transmit.  Common  salt  is  necessary  in 
the  process,  and  bile  greatly  aids  it.  Peptone  and  glucose 
are  thus  absorbed  from  the  intestine  by  every  point  of  its 
mucous  membrane.  The  millions  of  villi  projecting  into 
the  intestine  greatly  increase  the  surface  for  absorption, 

89 


90  APPLIED   PHYSIOLOGY 

while  their  thin  walls  are  especially  designed  for  the  easy 
passage  of  fluid. 


Diagram  of  the  course  of  food  in  its  absorption  and  assimilation. 

123.  Absorption  of  fat.  —  Fat  also  diffuses  in  the  alka- 
line solution  contained  in  the  intestine.  Under  the  micro- 
scope, particles  of  emulsified  fat  may  be  seen  inside  the 
epithelial  cells  of  the  villus.     Only  a  small  part  enters  the 


ABSORPTION   AND   ASSIMILATION  QI 

blood  tube  of  the  villus,  while  its  greater  part  enters 
the  lacteal  tube.  These  lacteals  unite  to  form  larger  and 
larger  tubes,  which  run  across  the  mesentery,  and  finally 
open  into  a  single  tube,  the  thoracic  duct,  running  up  the 
spinal  column.  This  is  a  tube  as  large  as  a  goose  quill, 
and  opens  into  a  large  vein  at  the  root  of  the  neck,  where 
emulsified  fat  from  the  intestine  first  reaches  the  blood. 

124.  Completion  of  digestion.  —  Reckoning  the  amount  of 
saliva  as  two  pints  a  day,  of  gastric  juice  as  eight  pints,  of  pancreatic 
juice  one  and  a  half  pints,  and  bile  as  two  pints,  and  of  food  three  pints, 
the  liquid  introduced  into  the  intestine  daily  amounts  to  two  gallons  at 
least,  and  nearly  the  same  amount  is  absorbed.  More  and  more  of  this 
liquid  is  absorbed  as  the  food  passes  down  the  intestine,  until,  about 
twelve  hours  after  eating,  w^hat  is  left  of  the  food  and  digestive  fluids 
reaches  the  large  intestine  in  a  semi-solid  state.  In  the  large  intestine 
absorption  and  peristalsis  are  so  very  much  slower,  that  from  twenty- 
four  to  thirty-six  hours  are  required  for  the  remains  of  food  to  traverse 
it.  Its  water  and  digested  food  and  some  of  the  bile  are  absorbed, 
while  the  rest  of  the  bile  and  its  other  waste  products  and  undigested 
matter  are  left  behind.  In  health  the  intestine  expels  the  waste  matter 
regularly  at  least  once  a  day. 

125.  Assimilation  of  fat.  —  Changing  the  digested  food 
into  the  various  fluids  and  tissues  of  the  body  is  assimila- 
tion. The  thoracic  duct  pours  the  digested  fat  into  a  large 
vein  on  the  left  side  of  the  neck,  whence  it  is  carried  with 
the  venous  blood  to  the  lungs.  Little  or  no  fat  can  be 
found  in  the  blood  leaving  the  lungs  unless  it  has  been 
eaten  in  excessive  quantities.  It  is  probably  oxidized  at 
once  to  carbonic  acid  and  water,  an  ounce  requiring  three 
ounces  of  oxygen.  It  is  unlikely  that  any  fat  from  the 
food  is  stored  up,  but  the  fat  in  the  body  is  probably 
derived  from  the  albumin  of  the  cells.  The  oxidation  of 
fat  produces  Jieat,  and  the  heat  may  be  changed  to  power, 
or  be  used  simply  to  warm  the  body. 


92  APPLIED    PHYSIOLOGY 

126.  Assimilation  of  glucose.  —  Glucose  enters  the  blood 
in  the  villi,  and  is  carried  from  there  to  the  liver  by  means 
of  a  large  vein  called  the  portal  vein.  As  the  blood 
emerges  from  the  liver,  it  contains  almost  uniformly  y-oVo" 
part  of  glucose,  no  matter  what  amount  of  sugar  is  in  the 
portal  vein.  The  liver  contains  a  sugarlike  substance 
called  glycogen,  which  increases  in  amount  after  digestion, 
and  almost  disappears  a  few  hours  after  eating.  So  it  is 
thought  that  glucose  is  stored  in  the  liver  as  glycogen,  and 
given  up  to  the  blood  in  a  steady  stream. 

In  the  blood  the  glucose  is  all  oxidized  to  carbonic  acid 
gas  and  water,  giving  out  heat  and  energy.  One  ounce  of 
glucose  requires  about  one  and  one  fifth  ounces  of  oxygen 
to  oxidize  it  completely. 

127.  Assimilation  of  peptone.  —  Peptone  is  a  poison  to 
the  body  and  must  be  changed  immediately  after  entering 
the  circulation.  It  is  carried  directly  to  the  liver  by  the 
portal  vein,  and  there  all  becomes  changed  back  to  forms 
of  albumin  which  will  not  diffuse  through  a  blood  tube, 
except  under  pressure.  The  liver  further  makes  the  albu- 
min a  living  part  of  the  blood.  Some  albumin  is  oxidized 
in  the  liver,  but  a  large  part  is  carried  to  the  cells  of  the 
body.  Each  cell  in  the  body  is  thus  bathed  in  albuminous 
food  brought  to  it  by  the  blood. 

Like  an  ameba,  each  cell  chooses  as  much  of  the  albu- 
min as  it  needs  for  food,  and,  taking  it  in  by  any  part  of 
the  surface  of  its  body,  makes  it  a  living  part  of  itself. 
Finally,  even  the  living  albumin  of  the  cell  is  oxidized,  an 
ounce  requiring  one  and  one  half  ounces  of  oxygen. 

128.  Absorbed  poisons  thrown  out  by  the  liver.  —  Fermen- 
tation in  the  intestine  produces  injurious  substances,  and 
the  bile  brings  in  waste  matter.  Decayed  food,  too,  con- 
tains poisons.     All  these  substances  may  be  absorbed  and 


ABSORPTION    AND   ASSIMILATION  93 

carried  to  the  liver,  which  either  destroys  the  poisons  or 
sends  them  back  to  the  intestine  along  with  the  bile.  In 
this  way  the  liver  is  a  continual  protection  to  the  body. 

129.  Summary  of  the  work  of  the  liver.  —  The  liver  serves 
as  the  7'egHlator  of  the  body.  The  bile  which  it  produces  is  to  the 
intestine  what  the  acid  is  to  the  stomach.  It  aids  the  action  of  the 
digestive  ferments  and  hinders  other  forms  of  fermentation.  It  smooths 
the  passage  of  food  down  the  intestine,  and  aids  diffusion  into  the  blood 
tubes.  The  liver  changes  digested  albumin  and  sugar  and  fits  them  for 
use  in  the  bloody  and  intercepts  poisons  which  may  be  circulating  in  the 
blood.  Its  work  goes  on  constantly,  and  upon  its  perfect  action  depends 
the  well-being  of  the  body. 

130.  Biliousness.  —  If  the  liver  acts  imperfectly,  a  part 
of  the  peptone  remains  unchanged ;  other  poisons,  too, 
brought  from  the  intestine  by  the  blood  are  not  destroyed  ; 
and  the  glucose  is  not  properly  assimilated  and  oxidized. 
A  coated  tongue,  headache,  loss  of  appetite,  and  an  uncon- 
querable feeling  of  dullness  follow,  and  are  symptoms  of 
what  is  known  as  bilioitsness. 

In  fevers  there  is  a  poisoning  of  the  body  by  the  cause 
of  the  disease.  As  the  liver  is  one  of  the  principal  organs 
which  remove  poisons  from  the  blood,  it  may  soon  be  able 
to  get  rid  of  them,  and  thus  cure  the  fever.  But  often  the 
task  is  too  great  for  it,  and  then  all  the  symptoms  of  a 
severe  bilious  attack  are  added. 

131.  Liver  medicines.  —  Certain  drugs,  like  77iercury  or  podo- 
phyllin,  have  the  power  to  increase  the  action  of  the  liver.  In  proper 
doses  they  cause  a  great  outpouring  of  bile  which  carries  with  it  the 
poisons  of  the  body.  The  drugs  also  cause  the  liver  cells  to  assimilate 
the  food  more  perfectly.  Thus  nature  is  assisted  by  the  drugs  and  the 
biliousness  is  soon  overcome. 

132.  Intestinal  indigestion.  —  When  the  stomach  is  over- 
worked and  acts  imperfectly,  its  work  is  thrown  upon  the 
intestine.     Digestion  there  is  imperfectly  accomplished,  and 


94  APPLIED    PHYSIOLOGY 

fermentation  takes  place,  with  the  development  of  poisons. 
The  gas  from  the  fermentation  causes  the  abdomen  to  swell 
or  bloat.  The  liver  is  imperfectly  nourished,  and  is  over- 
worked in  throwing  out  the  poisons;  so  it  fails  to  make 
the  proper  changes  in  food.  Then  the  whole  body,  in- 
cluding the  stomach,  is  weakened,  and  biliousness  is  pro- 
duced. At  last  nature  brings  on  severe  sickness,  and 
compels  the  overworked  organs  to  rest. 

133.  Prevention  of  biliousness.  —  Man  has  it  in  his  power  to 
prevent  almost  entirely  tlie  evils  of  indigestion.  He  should  eat  only 
plain  food,  in  moderate  quantities,  and  at  regular  intervals.  He  should 
be  careful  not  to  eat  when  he  is  tired,  or  heated,  or  just  before  or 
after  hard  work.  His  digestive  organs  would  then  furnish  a  continual 
supply  of  perfectly  digested  food,  sufficient  for  all  the  cells  of  the  body  ; 
the  influences  producing  disease  would  be  resisted  by  well-nourished 
cells,  and  sickness  would  be  rare. 

134.  Regularity  of  the  bowels.  — The  last  act  of  digestion, 
or  the  expulsion  of  waste  matters  from  the  intestine,  is  as 
important  as  eating,  and  should  be  performed  with  the 
same  regularity.  The  mouth  and  stomach  are  endowed 
with  feelings  which  make  known  their  needs,  but  the 
intestine  has  only  slight  sensibility,  and  we  are  unaware 
of  the  digestion  which  is  continually  going  on  in  it.  Only 
when  some  irritating  food,  or  a  large  collection  of  gas, 
greatly  increases  its  peristalsis  are  we  aware  of  its  action. 
At  a  regular  time  every  day  a  healthy  person  feels  that 
the  completing  act  of  digestion  should  be  performed,  but 
the  sensation  will  pass  away  if  it  is  neglected,  and  in 
course  of  time  the  sensation  will  be  repeated  only  once 
in  two,  three,  or  even  more  days.  The  retention  of  waste 
matter  all  that  time  cannot  fail  to  do  harm.  Even  if 
nature  does  not  give  the  sensation  indicating  the  need  of 
expelling  waste  matter,  the  matters  need  to  be  expelled. 


ABSORPTION   AND   ASSIMILATION  95 

and  the  opportunity  should  be  given  daily  at  a  regular 
time.  Even  if  little  food  is  eaten,  the  waste  matters  are 
still  formed,  and  need  expulsion.  It  should  be  remem- 
bered that  it  requires  two  days  for  food  to  pass  the  length 
of  the  intestine,  so  refraining  from  food  only  a  single  day 
does  not  make  the  intestine  empty. 

When  the  intestine  expels  its  contents  too  freely,  there 
is  usually  some  irritating  food  which  it  is  trying  to  expel. 
So  a  dose  of  medicine,  which  will  aid  in  its  expulsion,  is 
required  rather  than  something  which  will  restrain  the 
action. 

135.  Proper  food.  —  The  stomach  may  be  able  to  begin  digesting 
an  improper  meal,  while  the  intestine  is  unable  to  finish  the  work. 
Owing  to  the  slowness  with  which  the  intestine  acts,  several  meals 
may  be  eaten  before  its  failure  becomes  noticeable.  Then  the  last 
meal  is  blamed,  instead  of  the  offending  meal.  So  persons  may  gain 
wrong  ideas  about  the  digestibility  of  various  articles  of  food. 

136.  Headaches.  —  A  headache  is  generally  due  to  disturbances 
in  digestion.  Usually  when  the  liver  is  stimulated  by  a  proper  medi- 
cine, the  headache  ceases.  Even  if  the  headache  is  due  to  overwork, 
probably  it  would  not  have  come  on  if  the  digestive  organs  had  been 
performing  their  work  properly. 

SUMMARY 

1.  The  peptone  and  glucose  are  taken  up  by  the  epithelial 

cells  of  the  villi,  and  passed  on  to  the  blood  in  the 
capillaries  inside  the  villi. 

2.  Emulsified  fat  is  taken  up  by  the  epithelial  cells  of  the 

villi,  and  passed  on  to  the  lacteals  within  the  villi. 
From  there  it  goes  to  the  thoracic  duct,  and  finally 
is  poured  into  the  large  vein  at  the  root  of  the 
neck. 

3.  About  two  gallons  of  fluid  enter  and  leave  the  alimen- 

tary canal  each  day. 


96  APPLIED   PHYSIOLOGY 

4.  The  fat  is  carried  to  the  kings,  and  is  there  oxidized 

to  carbonic  acid  gas  and  water,  each  ounce  of  fat 
using  nearly  three  ounces  of  oxygen. 

5.  The  glucose  is  carried  to  the  liver,  and  from  there  is 

given  out  in  a  steady  stream  and  oxidized  to  car- 
bonic acid  gas  and  water,  each  ounce  using  a  little 
more  than  an  ounce  of  oxygen. 

6.  The    peptone    is    carried   to    the    liver,   and   there   is 

changed  back  to  the  form  of  albumin  adapted  to 
the  blood  and  tissues  of  the  body. 

7.  In  the  liver  some  albumin  is  oxidized,  and  the  rest  is 

sent  out  as  a  part  of  the  blood  to  feed  the  cells. 

8.  Poisons   are   often   absorbed  with    the   food,   and  are 

carried  to  the  liver.  But  the  liver  cells  separate 
out  the  poisons,  and  either  destroy  them  or  expel 
them  with  the  bile. 

9.  By   intemperate    eating   the    stomach    is   disordered. 

Then  more  work  is  put  upon  the  intestine,  until 
it  fails  in  its  duties.  Then  the  liver  has  imper- 
fectly digested  food  and  more  poisons  to  take  care 
of.  Then  a  poor  quality  of  bile  is  poured  out. 
Then  the  intestine  fails  still  more  in  its  work.  So 
the  circle  of  cause  and  effect  goes  on,  all  depending 
at  first  upon  intemperate  eating. 
10.  The  last  act  of  digestion,  or  the  expulsion  of  waste 
matters,  should  be  attended  to  regularly  every  day, 

DEMONSTRATIONS 

48.  Show  the  absorption  of  food  in  a  young  kitten  or  puppy 
which  had  been  fed  with  cream  about  two  hours  before  being  killed. 
Place  the  animal  in  a  tight  box  along  with  a  sponge  containing  half 
an  ounce  of  chloroform.  In  a  few  moments  the  animal  will  be  dead. 
At  once  open  its  abdomen  and  spread  out  its  intestine  Across  its 
fanlike  mesentery  will  be  seen  white  lines.     These  are  lacteals,  which 


ABSORPTION  AND   ASSIMILATION  97 

are  carrying  the  emulsified  fat  from  the  intestine.  The  fluid  looks 
like  milk,  and  so  the  name  lacteals,  or  milk  tubes,  was  given  to  the 
tubes.     (See  demonstration  35.) 

49.  Probably  some  boy  in  the  schoolroom  who  is  suffering  with  a 
bilious  attack  will  be  willing  to  show  his  tongue  to  the  class.  Notice 
that  it  is  covered  with  a  thick  white  or  yellow  fur.  Explain  that  the 
tongue  is  a  part  of  the  alimentary  canal,  and  that  the  stomach  and 
intestine  are  in  a  like  condition.  Explain  that,  when  the  rest  of  the 
alimentary  canal  is  acting  well,  the  tongue  is  clean  and  the  breath 
sweet. 

REVIEW  TOPICS 

1.  Describe  the  diffusion  of  digested  food  into  the  blood. 

2.  Trace  a  particle  of  digested  fat  from  the  intestine  to 

the  blood,  and  tell  what  finally  becomes  of  it. 

3.  Describe  how  the  liver  uses  digested  sugar. 

4.  Describe  how  digested  albumin  becomes  a  part  of  the 

blood,  and  tell  of  what  use  it  is  to  the  body. 

5.  Tell  how  the  liver  removes  poisons  from  the  absorbed 

food. 

6.  Tell  how  a  disturbance  of  digestion,  in  either  the  stom- 

ach, intestine,  or  liver,   disturbs   each   of  the   other 
organs. 

7.  Shov/  that  each  organ  of  digestion  is  perfectly  adapted 

to  its  own  work. 

OV.  PHYSIOL.  —  7 


CHAPTER   X 

ALCOHOL   AND  DIGESTION 

137.  Summary  of  the  action  of  alcohol. — The  action  of 
strong  alcohol  outside  of  the  body  is  threefold.  First,  it 
takes  away  water  from  substances  which  it  touches ;  sec- 
ond, it  hardens  and  coagulates  albumin ;  third,  as  a  result 
of  the  first  and  second  actions,  it  impairs  or  destroys  the 
life  of  cells  and  of  ferments  with  which  it  comes  in  con- 
tact. Alcohol  harms  the  body  in  these  ways  and  also  has 
special  effects  upon  parts  which  it  does  not  touch. 

138.  Effects  upon  food.  —  Alcohol  produces  changes  in 
food  in  direct  proportion  to  its  strength  and  amount.  If 
the  alcohol  be  strong,  and  large  enough  in  amount  to  satu- 
rate the  food,  then  it  may  harden  the  albumin  and  render 
it  more  difficult  of  digestion.  It  may  also  prevent  the 
pepsin  of  the  stomach  from  acting.  The  habitual  drunk- 
ard may  take  strong  drink  in  sufficient  amount  and  strength 
to  produce  this  change  in  his  food. 

139.  Effects  upon  the  mouth.  —  In  the  mouth  alcohol 
may 'take  water  from  the  epithelial  cells,  and  give  rise  to 
a  sense  of  thirst.  Although  the  alcohol  may  be  mixed 
with  enough  water  to  satisfy  natural  thirst,  yet  it  causes 
a  false  thirst  to  arise,  which  demands  another  drink. 

140.  Effects  upon  the  gastric  juice.  —  When  it  reaches 
the  stomach,  a  very  strong  alcoholic  drink  has  a  marked 
effect  upon  the  gastric  juice.  The  essential  digestive 
agent  in  the  gastric  juice  is  pepsin,  which  is  a  lifeless 
albuminous  ferment.     The  alcohol  in  any  common  form 

98 


ALCOHOL  AND   DIGESTION  99 

of  strong  drink  is  in  sufficient  quantity  to  hinder  or  to 
stop  the  digestive  action  of  the  pepsin.  But  when  the 
alcohol  is  absorbed  or  diluted,  the  pepsin  can  act  as  well 
as  ever. 

141.  Effects  upon  the  mucous  membrane. — Alcoholirri- 
tates  the  mucous  membrane  of  the  stomach.  Then  more 
gastric  juice  is  produced  in  order  to  dilute  the  irritating 
alcohol.  Thus  the  effect  of  the  alcohol  may  be  somewhat 
overcome  by  the  increased  quantity  of  the  digestive  fluid. 
But  the  alcohol  may  cause  an  increased  flow  of  mucus 
also,  just  as  a  cold  causes  the  pharynx  to  produce  more 
mucus.  The  mucus  may  coat  the  particles  of  food,  and 
prevent  the  gastric  juice  from  acting  on  them.  This  is 
especially  apt  to  happen  when  strong  drink  is  taken  con- 
tinuously in  small  amounts,  and  for  long  periods.  In  such 
conditions  both  the  quality  and  quantity  of  the  gastric 
juice  may  be  impaired. 

A  drink,  such  as  even  a  moderate  drinker  often  takes, 
may  produce  redness,  swelling,  and  inflammation  of  the 
stomach.  The  effect  is  far  greater  when  the  drink  is 
swallowed  upon  an  empty  stomach,  for  then  there  is  no 
food  to  protect  the  mucous  membrane  from  the  direct 
action  of  the  strong  drink. 

142.  Effects  upon  peristalsis.  —  The  irritation  of  the 
alcohol  at  first  causes  an  increased  action  of  the  stomach 
walls,  so  as  to  force  the  harmful  substance  away.  Con- 
tinuous use  of  strong  drink  is  likely  to  weaken  the  muscles 
and  to  make  peristalsis  much  less.  Then  the  food  is  less 
perfectly  mixed  with  the  gastric  juice  and  is  not  ground  to 
pieces,  but  remains  too  long  in  the  stomach  undigested. 
The  water  and  mucus  poured  out  diminish  the  strength  of 
the  alcohol,  and  this,  together  with  the  poor  quality  of  the 
gastric   juice   and  the  long  stay  of  food  in  the  stomach. 


lOO  APPLIED    PHYSIOLOGY 

permits  fermentation  to  take  place.  Thus  alcohol  disturbs 
every  action  of  the  stomach,  and  often  produces  the  worst 
forms  of  indigestion. 

It  is  true  that  a  little  weak  alcoholic  drink  will  not  produce  all  these 
evil  effects  at  once.  Herein  lies  the  danger.  Alcohol  is  a  deceitful 
thing.  Though  the  stomach  gives  notice  that  it  is  abused  by  the 
drink,  yet  the  mysterious  thirst  demands  still  more  alcohol,  and  bribes 
its  victim  with  the  memory  of  its  pleasant  sensation.  So  the  poor 
stomach  suffers  time  after  time,  and  before  long  becomes  permanently 
crippled. 

143.  Protection  against  alcohol.  —  When  an  alcoholic  drink  is 
taken  into  the  mouth,  it  irritates  the  mucous  membrane.  This  causes 
the  saliva  to  flow  and  dilute  the  alcohol,  so  that  at  any  one  time  it  can 
do  very  little  direct  harm.  In  the  stomach  it  causes  the  gastric  juice 
to  flow  in  the  same  way,  and  thus  it  soon  becomes  dilute  and  has  little 
direct  effect.  Even  if  the  pepsin  should  separate  from  the  gastric  juice, 
in  a  little  while  the  ferment  will  dissolve  in  the  increased  quantity  of 
juice  and  perform  its  work  well  again.  Nature  may  thus  protect  the 
body  for  some  time,  but  it  cannot  remove  the  danger. 

144.  Effects  of  alcohol  upon  the  intestine.  —  By  the  time 
alcohol  reaches  the  intestine,  it  is  usually  too  dilute  to 
produce  much  direct  harm..  But  if  it  has  deranged  stom- 
ach digestion,  the  work  of  digesting  the  food  falls  upon 
the  intestine.  Thus  intestinal  digestion  may  be  imperfect. 
Alcohol  itself  is  probably  not  changed  by  digestion.  In  its 
diluted  form  it  is  quickly  absorbed.  Even  when  a  large 
amount  is  absorbed,  little  or  none  can  be  found  in  any  of 
the  tissues  or  blood  tubes.  The  only  probable  way  of  its 
disappearance  is  by  oxidation  before  it  can  pass  beyond 
the  liver. 

145.  Effects  of  alcohol  upon  the  liver.  —  Alcohol  affects 
the  liver  in  three  ways.  In  the  first  place  strong  drink  is 
apt  to  induce  stomach  and  intestinal  indigestion.  Then 
the  liver  must  do  an  extra  amount  of  work  in  completing  the 
imperfect  digestion.     Thus  biliousness  is  often  produced. 


ALCOHOL  AND   DIGESTION  lOI 

If  drinking  is  continued,  the  liver  trouble  is  likely  to 
persist. 

In  the  second  place  the  destruction  or  oxidation  of 
alcohol  uses  a  large  amount  of  oxygen  which  the  liver 
should  use  in  assimilating  food.  Thus  food  is  imperfectly 
oxidized.  While  no  products  in  the  body  can  be  traced 
directly  to  oxidized  alcohol,  yet  when  alcohol  is  used  poi- 
sonous products  of  imperfectly  oxidized  albumin  are  always 
abundant.  These  products  circulate  through  the  whole 
body  and  produce  far  more  harm  than  the  original  alcohol. 
(See  p.  152.) 

In  the  third  place  the  liver  cells  are  directly  affected  by 
these  abnormal  actions.  Long-continued  drinking  often 
results  in  an  incurable  wasting  away  and  hardening  of  the 
liver  tissues. 

146.  Unintentional  forms  of  drinking.  —  There  is  a  form  of 
alcohol  which  is  used  by  many  innocently  and  unintentionally.  Many 
a  well-meaning  person  habitually  uses  "  Strengthening  bitters  "  after 
meals,  ignorant  of  the  fact  that  they  are  only  bitter  herbs  dissolved  in 
alcohol  and  water.     Each  dose  is  equivalent  to  a  large  drink  of  whisky. 

Essence  of  Jamaica  ginger  is  only  ginger  dissolved  in  alcohol,  and 
its  effects  are  due  mainly  to  the  alcohol,  and  not  to  the  ginger. 

147.  Intemperance  in  eating.  —  There  is  a  common  intem- 
perance of  eating  too  much  starch  and  sugar.  These  sub- 
stances can  never  be  digested,  absorbed,  and  oxidized  with 
sufficient  rapidity  to  produce  the  intoxicating  effects  of 
alcohol,  but  their  excessive  use  deranges  the  liver  in  the 
same  manner  as  alcohol.  In  the  first  place,  starch  and 
sugar  are  likely  to  ferment  and  produce  a  sour  stomach 
and  intestinal  indigestion ;  this  is  probably  the  most  com- 
mon cause  of  biliousness. 

In  the  second  place,  when  too  much  sugar  or  other 
food  is  oxidized  too  little  oxygen  is  left  for  the  albumin 


I02  APPLIED   PHYSIOLOGY 

of  the  food,  then  the  products  of  incomplete  oxidation 
resemble  those  produced  by  alcohol ;  but  they  usually  pro- 
duce no  more  than  a  sick  headache  or  an  attack  of  bilious- 
ness, although  under  aggravated  and  repeated  conditions 
they  may  endanger  life.     (See  p.  34.) 

In  the  third  place,  the  effect  of  a  continual  excess  of 
food  is  to  injure  the  liver  cells  permanently.  Even  the 
wasting  away  and  hardening  called  "gin  drinker's  liver" 
may  be  caused  by  intemperate  eating.  Intemperance  in 
eating  differs  from  the  intemperance  of  strong  drink  in 
the  quantity  of  effects  produced  rather  than  in  their  kind. 

SUMMARY 

1.  Alcoholic  drinks  take  water  from  the   mucous  mem- 

brane of  the  mouth  and  so  increase  the  thirst,  even 
if  the  body  contains  sufficient  water. 

2.  In  any  considerable  amount  alcohol  hardens  the  pepsin 

in  the  stomach,  and  so  prevents  its  acting  upon  the 
food. 

3.  Alcohol  irritates  the  mucous  membrane  of  the  stomach 

so  that  it  becomes  inflamed  and  unable  to  produce 
the  gastric  juice.  Then  the  intestine  is  overworked 
in  digesting  what  the  stomach  should  have  digested. 

4.  Alcohol  is   quickly  absorbed  by  the   intestine.      It  is 

quickly  destroyed,  probably  by  oxidation,  before  it 
passes  the  liver. 

5.  Because  oxygen  is  used  in  the  destruction  of  alcohol, 

incomplete  and  poisonous  products  of  the  oxidation 
of  albumin  are  formed.  These  go  through  the  whole 
body  and  greatly  increase  the  harm  done  by  alcohol. 

6.  Bitters,  and  essence  of  ginger  contain  much  alcohol. 

7.  When  starch  and   sugar  are   eaten   in   large  amounts, 

they  use  oxygen  which  should  oxidize  the  albumin. 


ALCOHOL  AND   DIGESTION  IO3 

So  they  can  produce  slowly  the  same  kind  of  effects 
as  alcohol. 

DEMONSTRATIONS 

50.  Hold  some  common  salt  in  the  mouth,  and  at  once  saliva  flows 
to  dilute  it.  In  a  moment  it  can  be  held  with  comfort.  Explain  that 
this  is  a  provision  of  nature  to  protect  the  body  from  any  irritating  sub- 
stance. The  stomach  may  pour  out  an  excess  of  gastric  juice  in  the 
same  manner  so  as  to  protect  the  body  against  alcohol  and  other  irri- 
tating substances.  Call  attention  to  other  similar  ways  in  which  nature 
protects  the  body,  as  in  the  flow  of  tears  to  wash  away  a  speck  of  dirt 
from  the  eyes. 

51.  Prepare  two  bottles  to  show  artificial  digestion  (see  demonstra- 
tion No.  40).  In  the  second  one  replace  a  quarter  of  the  water  with 
alcohol  and  notice  that  no  digestion  takes  place  in  this  bottle.  Explain 
that  this  experiment  may  be  misleading,  for  in  the  stomach  more  gastric 
juice  will  flow  to  dilute  the  alcohol  until  the  pepsin  can  act  as  well  as 
before.  Explain  that  alcohol  does  not  destroy  the  pepsin,  but  when  the 
alcohol  is  diluted,  the  pepsin  is  as  good  as  ever. 


REVIEW  TOPICS 

1.  Give  the  three  characteristic  actions  of  alcohol  outside 

the  body. 

2.  Give  the  action  of  alcoholic  drinks  upon  the  mouth. 

3.  Give  the  action  of  alcoholic  drinks  upon  the  mucous 

membrane  of  the  stomach ;  upon  its  secretions ;  and 
upon  the  peristalsis  of  the  stomach. 

4.  Tell  why  alcohoHc  drinks  have  but  little  direct  action 

upon  the  intestine  and  upon  the  villi. 

5.  Give  the  action  of  alcoholic  drinks  upon  the  liver. 

6.  Explain  why  bitters  and  essence  of  Jamaica  ginger  are 

both  harmful. 

7.  Explain  the  effects  of  intemperate  eating. 


CHAPTER   XI 

DIGESTION   IN  LOWER   ANIMALS 

148.  Digestion  in  dogs.  —  All  four-footed  animals  have 
essentially  the  same  digestive  organs,  secreting  the 
same  juices  as  man.  Their  food,  also,  is  absorbed  and 
assimilated  in  the  same  way,  but  there  are  slight  modifica- 
tions according  to  the  kind  of  food  eaten.  A  dog's  stom- 
ach and  intestine  have  thicker  walls,  and  their  juices  have 
far  more  digestive  power ;  so  dogs  can  digest  even  bones, 
which  form  one  of  their  regular  articles  of  diet. 

149.  Digestive  organs  in  cattle.  —  A  horse  lives  upon 
hay,  which  man  cannot  digest  at  all.  Cattle  have  an 
arrangement  which  enables  them  to  gather  a  large  amount 
of  food  at  once,  and  then  to  chew  it  at  leisure.  As  grass 
is  eaten,  it  is  swallowed  almost  whole.  It  gees  first 
to  a  small  intermediate  stomach,  and  then  to  a  large 
pouch  called  the  pauncJi  or  rumen,  which  in  an  ox  holds 
about  two  bushels.  When  this  is  full,  the  animal  lies 
down  and  proceeds  to  chew  the  food.  It  forces  the  food 
back  into  the  mouth  in  small  masses,  called  the  cud,  which 
it  chews  and  swallows  again.  But  this  time  the  food  is 
guided  on  to  a  third  stomach,  whence  it  soon  passes  into 
the  fourth.  The  fourth  stomach  corresponds  in  size  and 
shape  to  man's,  and  is  the  true  digestive  stomach,  while 
the  others  are  only  storehouses  and  passageways  for  the 
food. 

104 


DIGESTION  IN   LOWER  ANIMALS 


105 


150.  Digestive  organs  in  birds.  —  Birds  swallow  their 
food  whole,  for  they  have  no  teeth  or  strong  jaws  for 
chewing.  It  first  enters  a  pouch 
called  the  ci'op,  where  it  is  soaked 
in  a  fluid  secreted  there.  It 
slowly  passes  on  to  the  stomach, 
where  it  is  mixed  with  the  gastric 
juice.  Then  it  passes  into  a 
muscular  bag  called  the  giszard. 
The  walls  of  the  gizzard  are  from 
one  fourth  to  one  half  an  inch 
in  thickness,  and  its  lining  is  a 


thick,  tough  membrane.    It  con- 


Digestive  organs  of  a  bird. 
a  esophagus. 


b    craw,  or  crop. 
c   stomach. 
d  small  intestine. 
e   gizzard. 


tains  small   stones  which   have 

been  swallowed.    Its  thick  walls 

roll    the   food    about   with    the 

stones,  so  as  to  grind  it  to  pieces 

and  mix  it  with  the  gastric  juice. 

Then  it  passes  into  the  intestine,  where  its  digestion  is 

completed,  as  in  man. 

151.  Digestive  organs  in  insects  and  worms.  —  Insects 
possess  a  stomach  and  intestine  which  secrete  digestive 
juices.  They  also  have  organs  like  the  liver  and  pancreas. 
Some  insects  masticate  food,  and  others  possess  a  gizzard, 
which  grinds  the  food  after  it  is  swallowed. 

Worms  generally  possess  a  digestive  tube  which  extends 
straight  through  the  body.  Shellfish,  as  oysters  and  clams, 
possess  a  stomach  and  a  coil  of  intestine,  which  passes 
through  the  heart.  The  large,  dark-colored,  rounded  mass 
at  the  back  end  of  the  oyster  and  clam  is  the  liver. 

152.  Energy  required  in  digestion.  —  Man's  food  requires 
but  little  energy  in  its  digestion,  hence  most  of  his  energy  can  be 
applied  to  physical  and  mental  effort.     To  digest  dog's  food  requires 


I06  APPLIED   PHYSIOLOGY 

more  energy ;  to  digest  the  food  of  cattle  requires  still  more.  The 
lower  the  form  of  life,  the  more  time  and  energy  is  spent  in  digestion, 
and  the  less  is  the  action  of  other  parts,  until  the  lowest  forms  of 
animals  simply  live  to  eat,  and  remain  at  rest  except  when  eating  food. 
A  comparison  of  man's  digestion  with  that  of  the  lower  animals  is  mis- 
leading. Man's  alimentary  canal  is  designed  to  deal  with  food  upon 
which  but  little  energy  need  be  expended.  More  energy  is  thus  avail- 
able for  his  voluntary  use.  Because  of  his  perfect  food  man  can  per- 
form more  labor  and  undergo  more  fatigue  and  exposure  in  proportion 
to  his  size  than  any  other  animal. 

SUMMARY 

1.  The    digestive   organs    of   all    animals    are    similar   to 

man's,  but  modified  according  to  the  needs  of  the 
animal. 

2.  Cattle  swallow  grass  whole,  and  then  chew  it  at  leisure. 

They  have  four  stomachs. 

3.  Birds  swallow  food  whole.     It  passes  first  into  the  crop, 

and  later  is  ground  in  the  gizzard. 

4.  Insects,   worms,   and    shellfish  each   possess  a  simple 

stomach  and  intestine. 

5.  Man  uses  food  which  is  more  easily  digested  than  the 

food  of  any  lower  animal.     Thus   he   devotes    less 
time  to  mere  eating  and  digesting  food. 

REVIEW  TOPICS 

1.  Show  in  what  way  and  for  what  purpose  a  dog's  diges- 

tive organs  differ  from  those  in  man. 

2.  Show  the  use  of  four  stomachs  in  cattle. 

3.  Show  how  birds  digest  their  food. 

4.  Point   out  how  the   digestive  organs   are   modified   in 

worms  ;  in  insects  ;  and  in  shellfish. 

5.  Show  what  advantage  man's  food  gives  him  over  the 

lower  animals. 


CHAPTER   XII 
ANIMAL  FOOD 

153.  Food  elements.  —  Anything  which,  taken  inside  of 
the  body,  suppKes  it  with  weight,  heat,  or  energy  is  food. 
Man's  food  consists  of  a  great  variety  of  substances  de- 
rived from  the  animal,  vegetable,  and  mineral  kingdoms. 
Yet  all  food  consists  of  the  proximate  principles :  water, 
mineral  matter,  albumin,  fat,  and  starch  or  sugar.  Neither 
alone  makes  a  perfect  food,  but  all  must  be  present  in 
proper  proportions  or  else  the  body  will  suffer. 

154.  Water.  —  Water  requires  no  digestion,  but  is  con- 
tinually entering  and  leaving  the  body  unchanged  in  form. 
All  solid  food  contains  some  water,  and  enough  more  is 
added  in  liquid  food  and  in  drink  to  supply  the  full  needs 
of  the  body.  Twelve  or  fifteen  pints  of  fluid  are  used 
daily  in  the  work  of  digestion,  but  it  is  absorbed  back 
again  to  the  blood  and  so  little  is  lost.  Within  reasonable 
limits,  water  taken  at  mical  times  aids  digestion.  In  order 
to  digest  food  and  wash  away  waste  matter  properly,  two 
or  three  quarts  must  be  swallowed  daily.  If  the  thirst  is 
satisfied  with  pure  water,  there  will  be  Httle  danger  of 
taking  too  much,  and  the  indications  of  thirst  will  be  the 
most  reHable  guide  as  to  the  times  of  drinking  and  of  the 
quantity  required. 

155.  Mineral  matters.  —  Mineral  matters  are  not  changed 
during  digestion,  and  they  leave  the  body  in  the  same  form 
in  which  they  enter.     More  than  enough  are  found  in  all 

107 


I08  '  APPLIED    PHYSIOLOGY 

ordinary  food  to  supply  the  needs  of  the  body.  Only  salt 
needs  to  be  added  to  food,  but  man  often  adds  far  more 
than  is  necessary.  Since  water  and  mineral  matters  re- 
quire no  digestion,  it  makes  little  difference  in  what  kind 
of  food  they  are  eaten.  But  albumin,  fat,  and  starch  or 
sugar  require  digestion,  and  some  forms  are  more  easily 
digested  than  others,  so  a  discussion  of  their  forms  in  dif- 
ferent foods  becomes  necessary. 

156.  Digestibility  of  food.  —  In  judging  of  the  value  of 
food  four  things  must  be  considered : 

First.  The  time  and  energy  required.  —  Some  forms  of 
food  require  little  or  no  energy  in  their  digestion,  while 
others  cannot  be  digested  at  all.  Grass  contains  all  kinds 
of  food  substances,  but  man  cannot  digest  it.  The  com- 
bination of  meat,  fruit,  and  flour  which  we  call  mince  pie 
requires  far  more  time  and  energy  in  its  digestion  than 
the  same  substances  in  the  form  of  roast  meat,  bread, 
and  fresh  fruit,  or  in  the  form  of  a  light  pudding. 

Second.  The  amount  of  indigestible  matter.  —  All  kinds 
of  food  contain  some  matter  which  is  wholly  indigestible. 
Only  a  little  of  fruit  is  digested.  Careful  experiments 
show  that  ordinarily  at  least  one  fifth  of  the  albumin  of 
vegetable  food  passes  through  the  intestine  undigested, 
while  only  one  thirtieth  of  meat  is  thus  wasted.  Animal 
oil  is  easily  emulsified  and  saponified,  while  vegetable  oil 
can  scarcely  be  changed  at  all,  but  if  eaten  in  any  quantity 
is  a  source  of  intestinal  disturbance.  Some  wholly  indi- 
gestible matter  in  food  is  valuable,  for  it  affords  something 
upon  which  the  intestine  can  contract  so  as  to  force  its 
contents  down  the  tube. 

Third.  The  amount  of  energy  developed  by  the  food.  — ■ 
Fat  requires  a  large  amount  of  oxygen  in  its  oxidation, 
and  yields  a  large  amount  of  heat  and  energy.     Sugar 


ANIMAL  FOOD 


109 


requires  only  one  third  as  much  oxygen  and  develops  less 
heat  and  energy.  So  food  rich  in  fat  yields  more  heat 
and  energy  than  a  food  rich  in  sugar  or  starch. 

Fou7'th.  Liability  to  fennent.  —  A  food  requiring  a  long 
time  in  digestion  is  more  liable  to  ferment  than  one  which 
is  digested  in  a  short  time.  Sugar  and  starch  ferment 
easily,  while  fat  ferments  only  with  difficulty. 

157.  Milk.  —  Among  all  the  different  kinds  of  food  milk 
seems  to  be  most  perfectly  adapted  for  man  and  for  many 
animals.     The  average  cow's  milk  consists  of 

Water ^6  per  cent. 

Albumin 4         " 

Fat 4I 

Sugar 5 

Mineral  matter |-       " 

Milk  thus  contains  all  the  five  different  kinds  of  food 
substances,  which,  moreover,  are  in  about  the  proper  pro- 
portions to  support  life  best. 

The  albumin,  fat,  and  sugar  of  milk  each  re-         ^o    <»°^*^Oo 
quires  little  time  and  enero^y  in  its  digestion,  and        ^  o  ^VjoS  «^°  <= 

leaves  but  little  undigested  residue.     Milk  is  more  JD'-^  o  0  ^Aoq  Q 

liable  to  undergo  fermentation  than  some  other  o  OqQo^QPp^'o'' 

kinds  of  food,  but  the  quickness  of  its  digestion  **  q  '^'^Oo^OoCfo 
overcomes   this  objection.     It  develops  heat  and        oQOq*o?oo^ 

energy  in  amounts  best  suited  to  support  life,  p^^  globules  in  milk 
Milk  is  thus  an  ideal  food,  and  can  be  digested  (x  300). 

when  all  other  kinds  of  food  are  rejected. 

158.  Caseine. — The  albumin  of  milk  is  called  caseine. 
In  its  digestion  the  rennin  ferment  in  the  stomach  coagu- 
lates it  in  fine  flakes,  which  the  acid  and  pepsin  dissolve  to 
peptone.  When  much  acid  is  present  in  the  stomach,  as 
after  a  meal,  or  when  fermentation  has  occurred,  the 
caseine  is  apt  to  be  coagulated  in  hard  lumps  which  dis- 


no  APPLIED   PHYSIOLOGY 

turb  digestion,  producing  a  bilious  attack.  The  rennin 
ferment  is  produced  the  more  rapidly  when  milk  is  hot, 
while  the  heat  hinders  the  production  of  the  acid  of  the 
gastric  juice.  So  if  the  milk  is  taken  hot,  it  will  be  coagu- 
lated in  finer  flakes,  which  the  gastric  juice  can  digest  more 
easily.  If  milk  is  taken  slowly  in  any  form,  it  is  coagulated 
in  small  amounts  as  fast  as  it  enters  the  stomach,  and  so 
no  large  lumps  can  form.  If  taken  before  meals,  hot  and 
slowly,  there  are  but  few  persons  with  whom  milk  will 
disagree. 

159.  Fermentation  of  milk.  — Many  kinds  of  living  germs  are 
continually  falling  into  milk  and  growing,  if  the  temperature  is  warm. 
Some  are  germs  which  produce  acid  fermentation  and  turn  the  milk 
sour.  The  acid  coagulates  the  caseine,  forming  clabber.  Germs  of 
disease  also  will  grow  in  milk,  especially  germs  of  typhoid  fever  and  of 
tuberculosis.  Children  are  very  easily  affected  by  sour  milk.  Often 
the  germs  of  fermentation  grow  in  their  stomachs,  souring  the  food 
and  producing  su^nmer  co7)ipiaint.  Boiling  the  milk  destroys  the 
germs  but  not  the  poisons  which  already  have  been  produced.  All 
cow's  milk  given  to  babies  should  be  heated  in  order  to  destroy  the 
germs. 

160.  Cheese.  —  Rennet  is  often  added  to  milk  in  order  to 
coagulate  its  caseine,  which,  when  squeezed  into  a  firm 
mass,  is  cheese.  The  cheese  holds  the  fat  of  the  milk, 
while  the  sugar  remains  in  the  whey.  Cheese  is  about 
one  third  albumin.  It  contains  no  sugar  or  starch.  The 
amount  of  fat  which  it  contains  depends  upon  how  much 
cream  was  left  in  the  milk  of  which  it  was  made.  It  is  a 
valuable  article  of  food  because  of  the  large  amount  of 
albumin  always  present.  It  is  easily  digested  by  healthy 
persons.  In  some  kinds  germs  are  permitted  to  grow  and 
develop  various  acids  and  flavors  which  make  the  cheese 
strong.  These  are  somewhat  harmful,  but  mild  cheese  fur- 
nishes a  cheap  supply  of  good  albumin. 


ANIMAL   FOOD  III 

161.  Butter.  —  When  milk  remains  quiet  for  some  hours, 
the  fat  rises  to  the  surface  in  the  form  of  cream.  After 
this  is  removed,  milk  is  called  skhn  milk.  Cream  is  made 
up  of  fine  particles  of  fat,  each  surrounded  by  a  thin 
envelope  of  caseine.  When  cream  is  shaken  until  the 
covering  of  the  caseine  is  worn  off,  the  fat  collects  in  a 
form  called  butter.  The  liquid  part  remaining  is  called 
biittennilk,  and  does  not  differ  much  from  milk,  except 
that  the  fat  is  mostly  removed.  Butter  is  the  most  valu- 
able form  of  fat  eaten. 

162.  Value  of  milk. — In  sickness  milk  is  almost  the 
only  food  which  the  stomach  can  digest  at  all.  Only  about 
one  twentieth  of  the  solid  part  of  milk  fails  to  be  digested. 
When  only  milk  is  taken,  there  is  but  little  residue  upon 
which  the  intestine  contracts,  and  so  waste  matters  pass 
down  the  tube  more  slowly  than  when  solid  food  is  eaten. 
Those  who  eat  much  milk  find  it  profitable  to  eat  heartily 
of  substances  which,  like  oatmeal,  leave  a  large  undigested 
residue  to  sweep  out  the  waste  matters  of  the  intestine. 

163.  Adulteration  of  milk.  —  It  is  difficult  to  set  a  standard 
for  perfect  milk,  for  no  two  cows  give  it  of  exactly  the  same  composi- 
tion. Milk  which  has  a  good  quality  of  cream  usually  contains  a  good 
quantity  of  albumin  and  sugar  and  so  is  said  to  be  rich.  Such  milk  is 
yellow,  in  distinction  from  the  bluish  color  of  poor  or  skii)i  milk.  The 
richness  of  milk  may  be  measured  by  observing  how  thick  a  layer  of 
cream  will  rise  in  a  deep  glass  tube  full  of  milk.  Another  way  is  to 
determine  how  much  solid  matter  the  milk  contains  by  means  of  a 
lactometer .  This  is  a  closed  tube  weighted  so  that  it  will  float  upright. 
As  more  solid  matter  is  dissolved  in  the  milk,  it  becomes  heavier  and 
w'ill  more  easily  sustain  a  body  floating  upon  it.  The  richer  the  milk, 
the  less  the  bulb  and  tube  will  sink.  This  instrument  is  called  a 
lactojueter.  By  means  of  it  milk  brought  into  large  cities  is  tested  by 
government  inspectors,  and  all  milk  which  falls  below  a  certain  standard 
is  thrown  away.  The  lactometer  really  records  the  specific  gravity  of 
the  milk.     If  it  falls  below  1.029,  it  is  considered  to  be  either  w^atered 


112  APPLIED   PHYSIOLOGY 

or  of  too  poor  quality  to  be  sold  as  good  milk.  While  such  milk  may 
not  be  injurious,  yet  it  is  a  fraud  to  sell  it  at  the  price  of  good  milk. 
Skim  milk  is  bluish  in  color  from  the  loss  of  its  cream.  To  make  it 
the  color  of  new  milk,  burnt  sugar  is  often  added,  and  it  is  then  some- 
times sold  as  new  milk.  It  is  very  apt  to  become  sour  from  its  being 
kept  for  some  days. 

164.  Condensed  milk.  —  Large  quantities  of  milk  are  boiled 
until  its  water  is  evaporated  and  the  milk  is  like  thin  jelly.  This  is 
condensed  milk.  In  order  to  keep  it,  sugar  is  added.  Condensed  milk 
contains  all  the  nourishment  of  new  milk,  with  some  sugar  added.  It 
can  safely  be  used  in  place  of  new  milk  for  all  cooking  purposes.  It  is 
too  sweet  to  be  used  as  a  drink,  but  babies  take  it  readily.  Still  it  is 
undesirable  as  a  baby  food,  for  it  contains  too  much  sugar. 

165.  Imitation  cheese  and  butter.  —  Cheese  made  from  skim 
milk  contains  but  little  fat.  It  easily  ferments  and  becomes  dry,  so 
that  it  is  very  indigestible.  There  is  an  imitation  of  butter  made  from 
beef  fat,  called  oleojjiargarine.  It  scarcely  can  be  distinguished  from 
real  butter.  Butterine  is  another  imitation  of  butter  made  from  beef 
fat  and  butter.  The  manufacture  and  sale  of  both  kinds  of  imitation 
butter  are  permitted  so  long  as  the  products  are  sold  under  their  right 
names. 

166.  Eggs.  —  Hens'  eggs  consist  of 

Water JO  per  cent. 

Albumin 15         " 

Fat 14 

Mineral  matter i  " 

Since  they  contain  no  starch  or  sugar,  they  are  not  a 
complete  food  for  man,  although  a  perfect  chicken  may  be 
formed  out  of  the  ^g'g,  as  the  hen  furnishes  heat.  The 
white  of  ^^'g  is  almost  pure  albumin  dissolved  in  water. 
The  yolk  is  a  mixture  of  albumin,  fat,  and  water.  Both 
the  albumin  and  fat  of  eggs  are  digested  with  little  expend- 
iture of  time  and  energy,  and  develop  a  large  amount  of 
heat  and  energy  in  their  oxidation.  They  do  not  easily 
ferment  in  the  stomach  and  intestine,  and  only  about  one 


ANIMAL   FOOD  II3 

thirtieth  is  left  over  in  their  digestion.     They  are  thus  a 
valuable  food,  but  yet  do  not  rank  so  high  as  milk. 

167.  Digestion  of  egg  albumin.  —  When  boiled  for  a  minute 
or  two,  the  albumin  of  eggs  is  partly  coagulated  to  a  soft,  jellylike  mass. 
Boiling  for  three  minutes  coagulates  all  the  albumin  to  an  elastic, 
slippery  mass  ;  while  after  boiling  for  ten  minutes  the  albumin  becomes 
brittle,  and  is  easily  crushed  to  fine  particles. 

A  lump  of  albumin  of  a  raw  egg  is  digested  with  less  expense  of 
time  and  energy  than  the  same  sized  lump  of  coagulated  albumin,  and 
the  longer  an  egg  is  boiled  the  more  energy  is  required  to  digest  it 
back  to  a  liquid  form.  But  the  raw  egg  has  a  tendency  to  collect 
in  masses  which  the  gastric  juice  cannot  penetrate. 

An  egg  boiled  for  less  than  five  minutes  is  usually  masticated  only 
to  medium-sized  particles,  which,  however,  owing  to  their  smaller  size, 
may  be  digested  sooner  than  the  large  masses  of  raw  egg.  But  the  egg 
boiled  for  ten  minutes  is  easily  chewed  fine,  and,  owing  to  the  still 
smaller  size  of  its  particles,  is  digested  much  sooner  than  small  lumps 
of  soft-boiled  eggs  or  the  masses  of  raw  eggs.  Thus  an  egg  boiled 
for  at  least  ten  minutes  is  ordinarily  the  most  available  for  digestion. 
When  mixed  with  a  considerable  quantity  of  milk,  the  raw  egg  is  pre- 
vented from  forming  a  lump,  and  in  this  form  it  may  digest  more  easily 
than  a  cooked  egg. 

168.  Quality  of  eggs.  —  Fresh  eggs  vary  but  little  in  composi- 
tion. In  time  they  lose  a  little  water  by  evaporation  through  the  shell, 
which  is  porous.  A  fresh  egg  appears  clear  and  pink  when  held  in 
front  of  a  strong  light,  while  an  old  egg  appears  dark-colored,  even  if  it 
has  not  begun  to  decay.  It  will  first  show  a  dark  spot  where  the  yolk 
settles  to  the  side  of  the  shell,  and  later  will  be  dark  all  through.  This 
test  is  reliable  and  is  often  applied  in  markets.  The  shell  of  a  fresh 
egg  is  bright  in  color  and  slightly  rough  like  common  newspaper,  but 
an  old  egg  becomes  duller  in  color  and  shiny  in  appearance  like  writing 
paper.  Ducks'  eggs  are  nearly  like  hens'  eggs,  except  that  sometimes 
they  acquire  a  peculiar  taste  from  the  ducks'  food.  Nearly  all  kinds  of 
birds'  eggs,  as  well  as  the  eggs  of  turtles,  are  used  as  food.  They 
differ  but  little  from  hens'  eggs. 


'&&" 


169.    Meat  —  The  flesh  of  oxen,  sheep,  and  hogs  is  the 
common  form  of  meat.     All  kinds  of  game,  fowl,  fish,  and 

OV.  PHYSIOL. — 8 


114  APPLIED   PHYSIOLOGY 

shellfish  are  of  the  same  nature.  The  muscles  form  the 
lean  part  of  meat,  but  nearly  every  part  of  the  animal  is 
sometimes  used  as  food.     Average  meat  consists  of 

Water 65  per  cent. 

Albumin 17         ' 

Fat 14 

Mineral  matter 4 


(( 


Albumin  is  the  principal  part  of  .eat.  Beef  has  high 
food  value ;  mutton,  fowl,  and  game  rank  next,  in  the 
order  named. 

170.  Digestibility  of  meat.  —  Meat  varies  greatly  in 
composition  and  digestibility.  While  man  cannot  digest 
stringy  connective  tissue  and  tough  skin  at  all,  yet  good 
meat  ranks  next  to  milk  and  eggs,  and  exceeds  all  forms 
of  vegetable  food  in  all  the  four  points  of  digestibility.  It 
requires  a  small  outlay  of  time  and  energy  in  its  digestion, 
and  its  oxidation  develops  a  large  amount  of  heat  and 
energy.  It  does  not  easily  ferment,  and  only  about  one 
thirtieth  remains  undigested. 

Meat  is  often  salted  or  smoked  or  dried,  or  prepared  in 
other  ways  so  that  germs  of  fermentation  or  decay  will  not 
grow  in  it,  and  thus  it  can  be  kept  for  a  long  time.  When 
thus  prepared,  its  fibers  are  partly  coagulated  and  har- 
dened, so  that  the  gastric  juice  cannot  penetrate  them 
readily.  The  digestibility  of  such  meat  is  greatly  impaired. 
The  toughness  of  meat  is  due  to  strings  of  connective  tis- 
sue, which  are  digested  with  difficulty  and  yield  little  heat 
and  energy  to  the  body.  Tender  meat  consists  almost 
wholly  of  muscular  fibers,  which  are  the  main  nutritive 
parts  of  most  meat.  Since  meat  contains  no  starch  or  sugar, 
some  must  be  added  in  order  to  make  it  a  perfect  food ; 
and,  very  properly,  bread  is  generally  used. 


ANIMAL   FOOD  II5 

171.  Soup  and  beef  tea.  —  The  water  in  which  meat  is  cooked 
is  often  eaten  as  soup.  Soup  contains  some  gelatine  and  fat,  but  only 
a  small  amount  of  albumin,  for  most  of  the  albumin  is  coagulated  by  the 
heat,  and  thus  prevented  from  dissolving.  The  water  also  dissolves  the 
mineral  and  waste  matters  of  the  meat. 

Beef  juice  is  made  by  heating  the  meat  and  pressing  out  the  juice. 
The  best  meat  juice  contains  albumin  and  fat  in  about  the  same  pro- 
portions as  milk. 

Beef  tea  is  a  kind  of  concentrated  soup.  Mineral  and  waste  matters 
give  it  flavor.  It  is  very  poor  in  albumin  and  fat,  and  is  of  little  value 
as  a  food,  while  its  waste  matters  may  render  it  harmful.  There  are  no 
facts  to  warrant  the  assertion  that  beef  tea  contains  some  nutritious 
essence  of  the  meat  which  is  of  special  value  as  food.  Its  value  must 
be  judged  solely  by  the  amount  of  albumin  and  fat  which  it  contains. 
Extracts  of  meat  are  sold,  a  teaspoonful  of  which  added  to  a  cup  of 
water  is  said  to  contain  the  nourishment  of  a  pound  of  beef.  They 
consist  of  mineral  and  waste  matters  dissolved  in  water,  ana  so  are  of 
no  value  as  food.  Their  taste  may  be  pleasant,  and  this  may  assist  in 
the  digestion  of  other  food. 

172.  Fresh  meat.  —  As  a  rule  any  meat  is  most  whole- 
some if  it  is  eaten  soon  after  being  killed.  In  the  markets 
beef  is  usually  hung  in  a  room  whose  temperature  is  nearly 
freezing.  There  it  remains  fresh  for  weeks,  or  even  months, 
and  at  the  same  time  it  becomes  more  tender  and  improves 
in  flavor.  When  taken  out  and  exposed  for  sale,  it  spoils 
much  sooner  than  newly  killed  beef.  If  there  is  the  slight- 
est musty  or  decayed  odor  about  meat,  it  is  undesirable  as 
food. 

Game  animals  are  often  hung  just  as  they  are  killed, 
until  they  are  distinctly  decayed,  so  as  to  develop  peculiar 
flavors.  Fowl  and  game  are  liable  to  be  unwholesome  if  they 
are  kept  for  many  days  without  being  opened  and  cleaned. 

173.  Points  of  good  meat.  —  (i)  Tender  meat  usually  comes 
from  well-fed  animals,  and  such  animals  are  always  fat.  A  layer  of  fat 
from  one  fourth  to  one  half  inch  in  thickness,  covering  the  outside  of 
the  meat  just  under  the  skin,  usually  denotes  a  well-fed  animal.     The 


Il6  APPLIED    PHYSIOLOGY 

fat  will  also  extend  in  fine  white  streaks  irregularly  in  every  direction 
through  the  meat  and  can  be  clearly  seen  upon  its  cut  surface. 

(2)  The  fat  is  deposited  in  the  connective  tissue  which  incloses 
separate  bundles  of  muscles.  If  these  bundles  are  from  one  eighth  to 
one  fourth  inch  in  diameter,  and  preserve  their  shape  when  the  finger 
is  passed  over  them,  they  contain  much  connective  tissue,  and  the  meat 
is  tough,  as  in  meat  from  the  neck.  When  a  slice  of  such  meat  is 
gently  pulled  apart,  the  bundles  separate  from  each  other,  and  are  con- 
nected together  by  strong,  veil-like  meshes  of  connective  tissue. 

On  the  other  hand,  if  the  bundles  of  muscle  are  small  and  not  well 
marked,  the  connective  tissue  is  small  in  amount.  When  a  slice  of  such 
meat  is  pulled  apart,  its  bundles  do  not  separate,  but  the  whole  piece 
stretches. 

(3)  The  cut  edge  of  good  beef  soon  becomes  bright  red  in  color. 
When  the  connective  tissue  is  abundant  between  the  bundles,  it  im- 
parts a  paler  tint  to  the  meat,  and  sometimes  a  bluish  tinge.  Good 
pork  and  veal  are  pale  or  almost  white  in  color,  but  in  other  points 
resemble  beef  (see  p.  218). 

Good  meat  has  an  agreeable  odor  and  is  clean.  Excepting  as 
it  is  marked  by  connective  tissue  and  fat,  it  should  be  of  a  uniform 
tint. 

174.  Fish.  —  Fish  contains  albumin  about  sixteen  per 
cent,  fat  about  six  per  cent.  It  is  digested  with  rather  less 
ease  than  meat,  but  it  can  take  the  place  of  meat  as  food.  It 
used  to  be  thought  that  it  contained  more  nourishment  for 
the  brain  than  other  kinds  of  food,  but  the  brain  is  nour- 
ished by  the  same  substances  as  the  rest  of  the  body,  and 
fish  is  hardly  so  good  for  it  as  beefsteak. 

Fish  should  always  be  eaten  while  fresh,  for  it  is  espe- 
cially liable  to  decay. 

175.  Shellfish.  —  Shellfish,  as  oysters  and  clams,  contain 
about  sixteen  per  cent  of  albumin  and  three  per  cent  of  fat. 
The  large  dark  mass  in  their  bodies  is  the  liver,  which  con- 
tains some  sugar.  When  eaten  raw,  their  own  digestive 
fluids  and  their  livers  aid  in  the  digestion  of  their  bodies. 
When  cooked,  they  require  more  time  and  energy  for  their 


ANIMAL   FOOD  II7 

digestion.  Because  of  their  ease  of  digestion,  fresh  raw 
oysters  are  a  valuable  food  in  sickness.  Crabs  and 
lobsters  also  are  good  food  if  well  cooked. 

176.  Blood.  —  Blood  is  digested  with  difficulty.  It  contains  little 
albumin  and  fat  and  no  sugar.  It  adds  nothing  to  the  value  of  meat, 
and  is  very  Hable  to  decay.  It  should  always  be  removed,  as  is  usually 
done  in  killing  the  animal.  By  the  law  of  Moses  the  Jews  were  forbid- 
den to  eat  the  meat  of  animals  which  had  not  been  bled  to  death. 

177.  Inferior  meat.  —  Meat  cannot  be  adulterated,  but  inferior 
meat  is  sometimes  sold  as  good  meat.  Old  meat  is  sold  for  fresh  meat, 
and  tough  meat  for  tender.  Very  young  animals  are  dangerous  as  food, 
and  yet  they  are  often  sold.  Meat  from  sick  animals  is  always  unfit  for 
use.  In  France,  horseflesh  is  sold  for  food  under  its  own  name,  and  in 
this  country  it  is  sometimes  substituted  for  beef  in  cheap  shops. 

178.  Diseased  meat.  —  Meat  sometimes  contains  living  germs, 
which  may  produce  disease  in  those  who  eat  it.  The  most  common 
disease  to  be  feared  is  tuberculosis^  or  coiisiunption.  Beef  cattle  are 
especially  liable  to  have  the  disease,  which  may  be  located  in  their 
muscles  as  well  as  in  any  other  part  of  their  bodies,  and  is  difficult  of 
detection. 

A  tapeworm  passes  one  stage  of  its  existence  in  the  muscles  of  an 
animal.  Its  eggs  are  accidentally  eaten  by  an  animal,  and  develop  into 
minute  worms,  which  pass  through  the  walls  of  the  stomach  into  the 
muscles  and  there  form  white  cavities  about  the  size  of  a  pin  head, 
in  which  they  lie  quietly.  When  flesh  containing  such  a  w^orm  is 
eaten  and  digested  by  man,  the  worm  is  set  free  from  its  cavity,  and, 
fastening  itself  to  the  inside  of  the  intestine,  grows  to  many  feet  in 
length.  It  lays  eggs  which  will  grow  only  when  eaten  by  a  lower 
animal. 

In  pork  there  are  sometimes  found  microscopic  worms  called  trichiiicB. 
In  the  muscles  of  man  they  may  grow  and  multiply  enormously.  The 
disease  which  they  cause  is  both  painful  and  deadly.  It  is  extremely 
rare,  at  least  in  this  country. 

179.  Prevention  of  disease.  —  A  sure  preventive  against  any 
of  these  diseases  is  thorough  cooking,  for  heat  destroys  all  living  germs. 
It  has  not  been  proved  that  salting  and  smoking  meat  kills  the  germs 
in  it.  There  is  no  way  of  making  musty  or  spoiled  meat  fit  for  food. 
Such  meat  never  should  be  used. 


Il8  APPLIED   PHYSIOLOGY 


SUMMARY 


1.  Milk  is  the  most  easily  digested  and  most  perfect  of 

foods. 

2.  Hens'  eggs  contain  an  abundance  of  albumin  and  fat, 

but  no  starch  or  sugar.      They  are  next  to  milk  in 
ease  of  digestion. 

3.  Next  in  order  come  meats,  including  fish  and  shellfish. 

4.  Of  meats,  beef  has  high  food  value  ;  mutton,  fowl,  pork, 

game,  fish,  and  shellfish  rank  next,  in  the  order  named. 

5.  Animal  food  in  general  is  easily  and  quickly  digested 

and  only  about  one  twentieth  remains  undigested. 

6.  Meat  should  be  fresh  and  from  a  healthy  animal. 

DEMONSTRATIONS 

52.  Show  samples  of  fresh  milk  and  skim  milk.  Curdling  of  milk 
can  be  shown  by  adding  vinegar  to  milk  and  gently  stirring  it  until  the 
curd  collects  in  a  lump.  Show  that  this  is  cheese.  By  setting  some 
milk  aside  in  a  deep  bottle,  the  amount  of  cream  which  rises  can  be 
shown.  Butter  can  be  made  from  some  cream,  but  the  process  is 
uncertain,  especially  in  winter. 

53.  Test  some  milk  with  a  lactometer  or  a  specific  gravity  bulb.  In 
good  milk  it  should  sink  to  i  .030. 

54.  By  cutting  a  hole  in  a  piece  of  pasteboard  and  holding  eggs  in  it 
in  front  of  a  lamp  in  a  darkened  room,  contrast  the  bright  pink  of  a 
fresh  egg  with  the  dull  color  of  a  stale  egg,  as  is  done  in  testing  eggs 
in  the  market. 

55.  Show  some  fresh  meat  and  some  that  is  stale.  Show  some  very 
tender  and  some  very  tough  meat.  Show  that  the  toughness  of  meat 
is  due  to  white  strings  of  connective  tissue. 

REVIEW  TOPICS 

1.  Give  a  definition  of  food  and  tell  what  five  substances 

are  used  for  food. 

2.  Show  why  an  abundance  of  water  is  needed  in  food. 


ANIMAL   FOOD  -    II9 

3.  Show  why  salt  is  the  only  mineral  which  man  adds  to 

his  food. 

4.  Give  the  four  points  which  determine  the  digestibility 

and  value  of  a  food. 

5.  Show  that  inilk  is  a  perfect  food  and  how  it  may  be 

used  to  the  best  advantage,  and  how  to  avoid  dis- 
eases which  it  may  contain. 

6.  Show  how  to  distinguish  good  milk  from  poor,  and 

describe  two  methods  for  testing  it. 

7.  Describe  cheese. 

8.  Describe  butter  and  its  imitations. 

9.  Show  how  eggs  are  valuable  as  food  and  how  they  are 

deficient  and  how  they  had  best  be  eaten. 

10.  Show  how  a  good  ^^g  can  be  told  from  a  spoiled  one. 

11.  Show  how  ineat  is  valuable  as  food  and  how  it  is  de- 

ficient. 

12.  Compare  beef  tea  with  meat. 

13.  Compare  fresh  meat  with  meat  which  has  been  kept 

and  with  decayed  meat. 

14.  Describe  what  diseases  may  be  transmitted  by  meat, 

and  how  to  avoid  them. 

15.  Show  how  to  select  good  meat  in  the  market. 

16.  Show  how  fish  and  shellfish  resemble  meat. 


CHAPTER   XIII 
VEGETABLE   FOOD 

180.  Grain.  —  Food  prepared  from  grain  contains 

Albumin      ....  8  per  cent  to  15  per  cent. 

Starch  or  sugar    .     .  50         *'         to  75         " 

Fat I  *'         to  10         " 

Mineral  matter     .     .  i  "         to    3         " 

Some  forms  of  its  starch  or  sugar  are  digested  with  a 
considerable  expense  of  time  and  energy,  and  there  is 
always  a  considerable  portion  left  over.  From  grain 
nearly  all  the  starch  and  sugar  of  food  is  obtained. 

181.  Gluten.  —  The  albumin  of  most  grains  is  called 
gluten.  It  is  easily  dissolved  in  water  and  gives  the 
sticky  character  to  a  mixture  of  flour  and  water.  Its 
digestion  requires  an  expenditure  of  more  time  and  energy 
than  the  digestion  of  most  forms  of  animal  albumin,  but 
its  oxidation  yields  the  same  amount  of  energy.  About 
one  fifth  is  left  undigested,  whereas  only  one  thirtieth  of 
animal  albumin  is  left. 

The  husks  of  the  kernels  of  grain  and  the  cellulose  frameworks 
within  are  wholly  indigestible.  When  milk  is  digested,  there  is  little 
waste  matter  upon  which  the  intestine  can  contract.  A  food  like  grain, 
which  leaves  much  waste  matter,  furnishes  something  upon  which  the 
intestine  can  contract,  and  thus  sweep  the  waste  matters  on  and  out  of 
the  body.  For  this  reason  vegetable  food  is  of  use  aside  from  its 
nutritive  value. 

120 


VEGETABLE  FOOD  121 

182.  Fermentation  of  grain  in  the  alimentary  canal.  — 

Owing  to  its  large  amount  of  starch  and  sugar,  and  to  its  comparatively 
slow  digestion,  grain  foods  are  liable  to  ferment,  f'ermentation  will  be 
the  least  apt  to  occur  with  a  mixture  of  about  equal  parts  of  animal  and 
vegetable  food. 

183.  Bread.  —  Bread  is  the  most  common  form  of  food 
made  from  grain.  Usually  some  means  are  employed  to 
make  the  bread  porous  and  soft.  Yeast  is  commonly 
added.  Its  germs  grow  and  change  the  sugar  of  the  flour 
to  carbonic  acid  gas  and  alcohol.  The  gas,  bubbling 
through  the  wet  and  sticky  flour,  puffs  it  up  and  fills  it 
with  small  cavities,  whose  form  the  stiff  and  sticky  gluten 
preserves.  Corn  meal  has  but  little  gluten  to  make  it 
sticky,  and  so  it  will  not  preserve  enough  porous  character 
*;o  form  a  loaf  of  bread. 

Instead  of  yeast,  baking  pozvder  is  often  used  to  make 
bread  or  biscuit  ligJit.  The  powder  develops  carbonic  acid 
gas,  which  bubbles  through  the  dough.  Nearly  all  baking 
powders  are  minerals,  and  their  use  in  large  quantity  is 
undesirable. 

Bread  made  from  wheat  flour  requires  less  energy  in  its 
digestion  than  any  other  kind  of  vegetable  food.  Since 
some  starch  must  be  eaten,  bread,  in  combination  with 
milk,  eggs,  and  meat,  forms  the  best  diet  for  everyday 
use.    Rye  flour  makes  nearly  as  good  bread  as  wheat  flour. 

184.  Other  forms  of  grain  food.  —  Biscuit  is  bread  with  a 
little  fat  added  and  baked  in  small  lumps. 

Cake  is  a  mixture  of  flour,  eggs,  fat,  and  sugar.  A  large  amount  of 
fat  or  sho7'tening  tends  to  make  it  indigestible. 

Pajicakes  are  made  of  flour,  corn  meal,  or  buckwheat  flour.  If  they 
are  light  and  well  cooked,  they  are  of  as  much  value  as  bread. 

Cracked  wheat  and  other  preparations  of  wheat  are  often  boiled  in 
water,  forming  a  mush  or  pudding.  This  has  the  composition  and 
digestibility  of  bread. 


122  APPLIED   PHYSIOLOGY 

Cor 71  meal  boiled,  or  made  into  pancakes  or  corn  breads  is  almost  as 
easily  digested  as  wheat  flour.  It  contains  a  larger  amount  of  fat  than 
any  other  grain. 

Oatmeal  when  boiled  to  a  mush  is  a  very  popular  article  of  diet.  It 
requires  more  time  and  energy  in  its  digestion  than  any  other  common 
grain  food.  It  leaves  a  large  amount  of  undigested  residue,  which 
sweeps  out  other  waste  matters  as  it  is  forced  down  the  intestine. 

Rice  is  poorer  in  albumin  and  richer  in  starch  than  any  other  grain. 
But  when  animal  food  is  used  in  connection  with  it,  there  is  no  better 
combination  of  food,  for  it  is  the  equal  of  flour  in  digestibility. 

Barley  is  but  little  used  as  food  by  man.  It  contains  little  albumin 
but  a  large  amount  of  starch. 

185.  Ways  of  preparing  grain.  —  The  finest  grades  of  flour 

make  bread  which  is  digested  with  less  cost  of  energy  and  with  less 
residue  than  flour  from  the  whole  grain,  while  there  is  but  little  differ- 
ence in  the  amount  of  albumin  and  starch  which  they  contain.  Hot 
bread  is  injurious  only  when  it  is  moist  and  sticky  so  that  it  cannot  be 
chewed  to  fine  morsels.  Old  bread  is  more  easily  digested  than  new 
because  it  is  harder  and  drier,  and  so  can  be  chewed  fine. 

186.  Beans  and  peas.  —  Beans  and  peas  contain 

Albumin about  25  per  cent. 

Starch "60 

Fat "        2 

Their  albumin  has  much  the  same  composition  as  the 
caseine  of  milk,  and  is  called  leguniin.  It  requires  a  large 
expenditure  of  time  and  energy  in  its  digestion.  Both 
legui  lin  and  the  starch  are  very  liable  to  ferment  in  the 
intestine  and  produce  gases.  At  least  one  fifth  remains 
undigested.  Beans  and  peas  are  good  foods  for  an  out- 
door laborer  who  has  a  great  deal  of  spare  energy. 

187.  Potatoes.  —  Potatoes  contain 

Albumin 3  per  cent. 

Starch  or  sugar 22         " 

Water 75         " 


VEGETABLE  FOOD  12;^ 

They  are  very  poor  in  albumin,  but  rich  in  starch,  so  they 
go  well  with  meat  and  eggs.  Potatoes  require  a  greater 
amount  of  time  and  energy  in  their  digestion  than  bread 
and  yield  less  heat  and  energy,  and  leave  more  undigested 
residue,  and  are  more  liable  to  ferment. 

188.  Difference   between   animal   and  vegetable  food. — 

Animal  and  vegetable  foods  differ  in  several  particulars  : 

First.  Animal  food  requires  less  energy  in  its  digestion.  Animal, 
rather  than  vegetable,  food  is  light  diet. 

Secojid.  Because  of  its  longer  time  of  digestion,  and  of  the  larger 
amount  remaining  undigested,  vegetable  food  is  more  liable  to  ferment 
in  the  stomach  and  intestine,  so  that  in  severe  sickness  vegetable  food 
is  usually  entirely  withheld. 

Thi7'd.  Vegetable  food  alone  contains  too  much  starch  and  sugar 
for  the  needs  of  the  body.  Fermentation  is  thus  promoted.  When 
absorbed,  sugar  is  more  readily  oxidized  than  fat  or  albumin,  and  an 
excess  of  sugar  takes  oxygen  from  other  parts  of  the  body. 

189.  Special  use  of  vegetable  food.  —  While  animal  albu- 
mins and  fats  are  more  easily  digested,  and  furnish  a  greater 
suppl}'  of  heat  and  energy  than  the  same  kind  of  food  of 
vegetable  origin,  it  by  no  means  follows  that  man  should 
use  them  to  the  exclusion  of  vegetables.  Their  very  ease 
and  completeness  of  digestion  may  lead  one  to  eat  too 
much.  Man's  mouth  and  stomach  combine  the  character- 
istics of  herbivorous  and  carnivorous  animals,  and  he  will 
enjoy  the  best  health  when  both  classes  of  food  are  used. 
He  must  use  some  vegetable  food  for  the  sake  of  its  starch 
or  sugar. 

190.  Effect  of  cooking.  —  The  distinctions  between  food 
just  given  were  based  upon  experiments  made  upon  healthy 
men,  who  ate  slowly,  and  masticated  food  properly  cooked. 
All  vegetable  food  should  be  cooked  so  that  it  is  a  dry  and 
crumbly  mass  which  the  digestive  juices  can  easily  pene- 


124  APPLIED   PHYSIOLOGY 

trate.     Thorough  cooking  renders  all  kinds  of  food  more 
digestible.     Raw  starch  is  indigestible. 

191.  Green  vegetables.  —  There  are  many  kinds  of  vege- 
table food  which  supply  little  weight,  heat,  or  energy  to 
the  body,  yet  are  often  eaten  because  of  their  agreeable 
taste.  Beets,  turnips,  carrots,  parsnips,  pumpkins,  and 
melons  are  poor  in  albumin.  They  contain  some  starch 
and  sugar  and  much  fibrous  substance  wholly  indigestible. 
Their  agreeable  taste  may  increase  the  flow  of  the  diges- 
tive fluids,  and  their  bulk  may  excite  the  peristalsis  of  the 
intestine. 

Tomatoes,  cabbage,  cauliflower,  onions,  asparagus,  and 
all  other  green  vegetables  are  still  poorer  in  food  mate- 
rial, and  are  especially  liable  to  ferment  in  the  intestine. 

Green  vegetables,  such  as  cucumbers,  which  are  eaten 
in  an  unripe  state,  are  wholly  indigestible.  Thus  they 
may  pass  through  the  intestine  almost  unchanged,  or  they 
may  ferment  and  produce  pain. 

192.  Iron  in  vegetables.  —  Green  vegetables  contain  a 
considerable  quantity  of  iron-bearing  albumin  or  nucleo- 
albumin,  while  grain  and  animal  food  contain  only  a  small 
quantity.  This  form  of  albumin  is  easily  destroyed  in  the 
intestine  if  fermentation  of  food  takes  place.  Under  these 
circumstances  green  vegetables,  by  furnishing  an  abun- 
dance of  this  material,  are  a  real  food.  Those  should 
be  chosen  wh^ch  do  not  readily  ferment.  Of  them  all, 
probably  celery  and  spinach  are  best. 

193.  Fruit.  —  Fruits,  such  as  apples,  pears,  plums, 
peaches,  and  berries,  have  little  albumin  which  man  can 
digest,  but  often  have  a  large  amount  of  sugar.  Their 
chief  use  is  to  fill  the  intestine  when  a  food  is  eaten 
which,  like  milk,  leaves  but  little  undigested  matter  to  sweep 
along  with  the  bile  and  other  waste  matters.     But  all  fruits 


VEGETABLE   FOOD  1 25 

are  liable  to  ferment  in  the  intestine.  Grapes  contain 
more  albumin  than  almost  any  other  fruit,  while  their 
sugar  is  the  form  produced  by  digestion.  For  these 
reasons  they  are  easily  digested,  and  are  a  real  food. 
Bananas  also  contain  much  albumin  and  sugar.  Green 
fruit  is  digested  with  difficulty  and  is  very  liable  to  injure 
the  stomach.  Over-ripe  and  decayed  fruits  often  contain 
poisons  which  produce  violent  sickness.  Only  a  small 
quantity  of  any  fruit  should  be  eaten  at  once. 

194.  Tart  fruits.  —  Oranges,  lemons,  rhubarb,  and  such  tart  or 
sour  articles  of  food  are  often  said  to  be  "  cooling ''  to  the  blood.  When 
the  appetite  fails,  and  the  mouth  is  dry  with  a  false  thirst,  their  sourness 
excites  the  flow  of  the  alkaline  saliva,  and  so  the  mouth  and  tonerue 
become  moist,  and  the  false  thirst  is  relieved.  In  long  voyages  and 
expeditions,  when  fresh  food  cannot  be  obtained,  they  are  of  value  in 
warding  off  scurvy.  When  eaten  at  meal  times,  the  acid  of  sour  fruits 
hinders  the  production  of  the  gastric  juice,  and  thus  retards  rather  than 
aids  digestion.  In  the  stomach  the  acids  unite  with  the  mineral  matters 
of  the  food,  and  then  are  absorbed  into  the  blood.  Their  presence  in 
the  blood  seems  to  have  some  effect  on  the  nutrition  and  action  of  the 
cells,  and  on  this  account  they  are  sometimes  given  as  medicine.  They 
seldom  take  part  in  building  up  the  body,  but  are  quickly  thrown  off 
by  the  kidneys.  The  popular  idea  of  their  cooling  effect  is  derived 
mainly  from  the  fact  that  they  excite  the  flow  of  saliva,  and  thus  render 
the  mouth  moist. 

195.  Nuts.  —  Nuts  contain  oil,  but  it  is  doubtful  if  much 
of  it  is  emulsified  and  absorbed.  They  contain  an  abun- 
dance of  albumin  and  starch,  but  their  digestion  usually 
requires  more  time  and  energy  than  the  stomach  of  man 
is  designed  to  furnish. 

196.  Canned  food. — When  food  is  heated  so  as  to  destroy  its 
living  germs,  and  then  is  at  once  sealed  air-tight,  it  will  neither  decay 
nor  sour,  and  when  opened  a  long  time  afterwards  it  will  be  found  to  be 
as  fresh  and  wholesome  as  when  it  was  put  into  the  can.  Thus  it  is 
possible  to  carry  fresh  meat  and  vegetables  on  long  voyages  or  to  remote 


126  APPLIED   PHYSIOLOGY 

and  cold  countries.     When  carefully  prepared,  canned  food  is  as  whole- 
some as  food  recently  cooked.     When  opened  it  soon  spoils. 

197.  Scurvy.  —  When  men  have  been  living  for  months 
upon  bread  and  salt  meat,  without  fresh  food,  there  some- 
times comes  a  disease  called  sciu'vy.  The  gums  become 
sore,  and  the  legs  ache  and  turn  ^^  black  and  blue''  as 
though  they  were  bruised.  Then  fruit  or  green  vegeta- 
bles are  of  the  highest  value,  probably  because  they  fur- 
nish a  good  supply  of  micleo-albinnin,  in  which  old  bread 
and  salt  meat  are  apt  to  be  deficient. 

198.  Seasonings.  —  Pepper,  mustard,  nutmegs,  cloves,  and  all  such 
sharp-tasting  things  are  added  to  food  simply  for  their  taste.  They  are 
probably  neither  digested  nor  oxidized,  and  yield  neither  weight,  nor 
heat,  nor  energy.  They  irritate  and  burn  the  stomach  just  as  they  do 
the  mouth.  Yet  their  pleasant  taste  may  be  of  value  in  promoting  the 
flow  of  the  digestive  juices. 

199.  Tea  and  coffee.  —  Tea  and  coffee  are  often  sup- 
posed to  supply  food  to  the  body.  They  belong  to  the 
class  of  substances  which,  acting  through  the  nervous 
system,  spur  on  the  work  of  the  cells  of  the  body,  espe- 
cially of  the  brain.  They  supply  no  heat  or  energy  for 
the  extra  exertion.  Substances  which  excite  the  cells  to 
action,  without  giving  them  material  out  of  which  to 
develop  heat  and  energy,  are  stimulants.  The  active 
principle  of  tea  and  coffee  is  a  stimulating  substance 
called  caffeine  which  spurs  the  cells  of  the  body  to  do 
more  work.  They  enable  a  person  to  do  a  larger  amount 
of  work  iji  an  etnerge^tcy,  and  when  the  body  is  tired  they 
rouse  the  digestive  and  assimilative  organs  to  renewed 
activity,  so  that  these  quickly  prepare  a  new  supply  of 
food.  When  they  are  used  continually  the  body  learns  to 
rely  upon  their  stimulation.  Thus  a  habit  of  drinking  them 
is  formed  which  is  not  easily  broken. 


VEGETABLE  FOOD  12/ 

200.  Tannin.  —  Coffee  and  tea  also  contain  some  ta7i- 
nin,  which  is  a  substance  used  in  the  manufacture  of 
leather.  It  puckers  and  contracts  albumin  with  which 
it  comes  in  contact,  and  is  liable  to  hinder  digestion. 
Much  of  the  bad  effect  of  strong  tea  is  due  to  its  tannin. 

201.  Volatile  oils.  —  Both  tea  and  coffee  also  contain  a 
considerable  quantity  of  an  oil,  which  gives  the  drinks  their 
peculiar  odors  and  flavors,  but  which  evaporates  quickly. 
It  is  mainly  this  oil  which  produces  headache  and  sleep- 
lessness and  other  troubles,  when  large  quantities  of  tea  or 
coffee  are  taken.  Yet  both  drinks  agree  with  the  stomach 
better  when  the  oil  is  retained  in  the  drink. 

202.  Preparation  of  tea  and  coffee.  —  Both  the  caffeine  and 

the  oil  of  tea  and  coffee  are  easily  dissolved  b}'  boiling  water,  but  by 
long  boiling  the  volatile  oil  is  driven  off  in  the  vapor,  and  a  large 
amount  of  tannin  is  extracted.  Both  these  results  are  undesirable,  and 
can  be  avoided  by  pouring  boiling  water  over  the  tea  and  coffee,  and 
then  steeping  it  slowl}'  for  only  a  few  minutes. 

Coffee  will  be  digested  more  easily  if  the  milk  which  is  added  is 
boiled  nith  the  coffee.     Better  still  would  be  to  add  no  milk  at  all. 

203.  Adulteration  of  tea  and  coffee.  —  It  is  easy  to  add  the 
leaves  of  other  plants  to  tea  leaves.  Green  teas  are  often  colored  with 
copper. 

Coffee  is  adulterated  with  all  kinds  of  roasted  roots.  A  root  called 
chicory  is  cultivated  especially  for  this  purpose. 

204.  Cocoa.  —  Cocoa  contains  a  small  quantity  of  a  sub- 
stance which  stimulates  like  caffeine.  It  also  contains  a 
considerable  quantity  of  albumin  and  fat,  both  of  which 
will  dissolve  in  water.  Thus  it  is  more  of  a  food  than  tea 
or  coffee,  and  its  use  is  less  likely  to  cause  indigestion. 
Chocolate  is  a  preparation  of  cocoa. 

205.  Use  of  tea  and  coffee.  —  Tea  and  coffee  are  not 
necessities,  and  men  would  be  just  as  healthy  without 
their   use.     They  have    a   reputation   of    retarding  waste 


128  APPLIED   PHYSIOLOGY 

of  the  body,  but  this  view  is  not  founded  upon  definite 
experiments.  The  nervous  system  of  children  is  easily 
impressed  by  tea  and  coffee,  and  their  bodies  cannot  stand 
the  stimulation  and  extra  work  which  these  substances 
induce.  When  long  and  fatiguing  work  must  be  done  or 
great  exposure  endured,  then  tea  and  coffee  are  valuable 
stimulants. 

206.  Adaptation  of  man's  stomach  to  certain  foods.  — 
Green  vegetables,  fruit,  and  grass  contain  the  proper 
quantities  of  food  elements  to  support  man's  life,  but 
man  cannot  digest  them  readily.  Lower  animals  eat  the 
food  and  expend  their  digestive  energies  on  it ;  finally, 
when  man  eats  it  in  the  form  of  milk,  eggs,  or  meat,  i1 
needs  but  little  further  digestion. 

SUMMARY 

1.  Grain  is  the  main  source  of  vegetable  food. 

2.  Grain  albumin,  or  gluten,  is  digested  at  more  expense 

of  time  and  energy  than  the  albumin  of  animal  food. 

3.  Grain  food  contains  much  starch,  and  must  be  eaten 

to  supply  this  element. 

4.  Grain  food  is  more  liable  to  ferment  than  animal  food. 

5.  Bread  is  the  form  of  grain  most  available  for  digestion. 

6.  Boiled  preparations  of    grain  contain  the  same  food 

elements  as  bread. 

7.  The  most  valuable  of   the    grains  which  are  usually 

eaten  boiled  are  rice,  cracked  wheat,  corn  meal,  and 
oatmeal. 

8.  Cake  and  biscuit  may  be  considered  as  forms  of  bread. 

9.  Beans  and  peas  are  rich  in  albumin  and  starch,  but 

require  a  great  deal  of  energy  in  their  digestion. 
10.    Potatoes  are  poor  in  albumin  but  rich  in  starch.     Their 
digestion  requires  much  energy. 


VEGETABLE   FOOD  1 29 

11.  Animal  food  in  general  fulfills  the  points  of  digestibil- 

ity better  than  vegetable  food. 

12.  Green  vegetables  and  fruit  are  of  value  because  their 

taste  may  excite  the  flow  of  digestive  fluids  ;  the 
large  residue  left  after  their  digestion  may  sweep 
waste  matters  down  the  intestine ;  and  they  may 
form  a  supply  of  nucleo-albumin  when  the  supply 
in  ordinary  food  is  deficient. 

13.  Green  vegetables  and  fruit  should  be  eaten  a  little  at 

a  time,  because  of  their  great  liability  to  undergo 
fermentation. 

14.  Tea,  coffee,  and  cocoa  spur  the  cells  on  to  renewed 

activity  when  the  body  is  tired  or  weakened. 

DEMONSTRATIONS 

56.  Grain  albumin,  or  gluten,  can  be  separated  by  mixing  a  small 
mass  of  dough  of  wlieat  flour  and  gently  washing  out  the  starch  by 
kneading  it  under  water.  The  gluten  will  be  left  as  a  stringy,  sticky 
mass.     The  starch  in  grain  can  be  shown  by  the  iodine  test  (page  31). 

57.  Show  samples  of  bread,  both  light  and  heavy,  sweet  and  sour, 
well-baked  and  under-done,  new  and  stale,  and  hot  and  cold.  Show 
that  the  difference  between  the  last  three  pairs  depends  upon  the  one 
kind  forming  a  pasty  mass  when  wet  cr  chewed,  while  the  other  kind 
may  be  broken  into  fine  particles. 

58.  Show  samples  of  properly  cooked  and  of  improperly  cooked 
rice,  oatmeal,  etc. 


REVIEW  TOPICS 

Give  the  composition  of  gram. 
Describe  the  albumin  of  grain. 
Describe  bread  and  the  process  of  its  manufacture. 
Describe  foods  which  are  like  bread. 
Describe  the  various  kinds  of  grain  which  are  eaten 
when  boiled  to  a  mush. 

OV.  PHYSIOL.  —  Q 


130  APPLIED   PHYSIOLOGY 

6.  Give   the   difference    of    digestibility   between   bread 

made  from  unbolted  and  fine  flour;  between  hot 
and  cold  bread ;  between  new  and  old  bread. 

7.  Give  a  reason  why  grain  food  should  not  be  sweetened. 

8.  Describe  beans  ^.n&peas. 

9.  Describe  potatoes. 

10.  State  why  the  method  of  cooking  and  the  manner  of 

eating  make  a  great  difference  in  the  value  of 
vegetable  foods. 

11.  Give  the  main  points  of  difference  between  animal 

and  vegetable  foods. 

12.  Name  the  food  elements  in  green  vegetables  and  jn 

fruits. 

13.  Give  the  important  uses  of  green  vegetables  and  fruits. 

14.  Tell  how  green  vegetables  and  fruits  should  be  eaten. 

15.  Show  that  man's  stomach  is  adapted  to  certain  kinds 

of  food  only,  and  tell  how  all  kinds  of  food  may 
ultimately  become  adapted  to  his  use. 

16.  Give  the  active  principles  of  tea,  coffee,  and  cocoa, 

and  the  effects  of  each  upon  the  body. 

17.  Name  the  food  elements  in  milk;  in  eggs;  in  meat; 

in  grain  ;  in  potatoes  ;  in  beans. 

18.  Give  the  organ  in  which  each  of  the  following  foods 

are  acted  upon,  the  digestive  fluids  which  act  upon 
it,  and  the  chemical  change  produced  by  each  fluid: 
milk,  eggs,  meat,  bread,  butter,  grain  food,  potatoes, 
beans. 


CHAPTER    XIV 
QUANTITY  OF  FOOD   REQUIRED 

207.  Amount  of  food  elements  required.  —  Although 
oxidation  is  continually  going  on  in  each  cell  of  the  body, 
only  a  small  part  of  the  albumin  eaten  is  required  in  their 
reconstruction  ;  the  remainder  and  all  the  sugar  and  fat 
are  oxidized  without  ever  becoming  a  part  of  the  living 
cells  of  the  body. 

In  order  to  repair  the  waste  caused  by  the  oxidation  of 
the  cells,  and  to  supply  the  requisite  amount  of  heat  and 
energy,  the  average  man  must  assimilate  daily  — 

Albumin 4^  ounces 

Fat 4 

Sugar  or  starch 5  " 

208.  Amount  of  oxygen  required.  —  The  amount  of  oxy- 
gen needed  to  oxidize  the  — 

Albumin     is  i-|-  times  its  own  weight,  or  6.3  ounces 
Fat  3       "  "  "  12 

Sugar  il     "  "  "  6 

Total  amount  of  oxygen  required  daily,  24.3  ounces 

The  average  amount  of  oxygen  taken  in  daily  by  the  lungs 
is  twenty-four  ounces.     When  more  food  is  eaten  than  this 
amount  of  oxygen   can   oxidize,  some  of  the  albumin  is 
changed  to  fat,  which  increases  the  weight  of  the  body. 
Anything  which  causes  the  lungs  to  take  in  more  oxygen 

131 


132 


APPLIED   PHYSIOLOGY 


will  enable  the  body  to  oxidize  more  food.  So  the  laborer 
breathing  deeply  of  fresh  air  is  less  troubled  with  the  bad 
effects  of  over-eating  than  a  clerk  in  an  office. 

209.  Oxidation  of  an  excess  of  sugar.  —  Sugar  is  more 
rapidly  oxidized  than  other  food,  and  when  too  large  a 
proportion  of  starch  or  sugar  is  eaten  the  other  food  is 
incompletely  oxidized,  and  sickness  is  the  result.  A 
greater  proportion  of  starch  is  required  when  more  heat 
and  energy  are  needed,  as  in  physical  labor. 

210.  Selection  of  diet.  —  To  supply  the  proper  elements, 
a  variety  of  food  may  be  selected,  of  which  the  following 
diet  for  twenty-four  hours  is  a  typical  example. 


Oz.  OF 

Albumin. 

Oz.  OF 

Fat. 

Oz.  OF 

Sugar. 

7     ounces  of  bread      contains     .     .     . 

3-5  ''  eggs  (2)  '^  ... 
14  "  meat  "  1.  .  . 
24            "          milk(iipt.)  ''          ... 

1.5         "          butter             "          ... 

0.7 
0.5 
2.5 
0.9 
0 

0 

0.5 
2 

I 

1-5 

4.2 

0 

0 

1.2 

0 

Total 

4.6 

5 

5-4 

Allowing  for  the  amount  usually  left  undigested,  there 
would  remain  about  the  proper  amount  of  each  kind  of 
food  element.  This  food  contains  more  than  enough  min- 
eral matter  to  supply  all  the  needs  of  the  body. 

211.  Choice  of  food.  —  The  price  of  food  has  little  to  do 
with  its  nourishing  qualities.  Fine  taste,  good  appearance, 
and  rarity  are  usually  what  make  foods  costly.  The 
cheaper  kinds  are  quite  as  nourishing  as  the  more  fashion- 
able, and  will  taste  as  good  if  they  are  well  cooked.  About 
three  fourths  of  a  laborer's  wages  are  spent  for  food. 
Cheaper  meats  and  fish,  with  less  sugar  and  desserts,  will 


QUANTITY   OF  FOOD   REQUIRED  1 33 

furnish  him  a  better  diet,  and  at  less  cost.  It  is  as  bad 
economy  for  a  poor  man  to  buy  the  best  of  food  as  it  is  for 
him  to  buy  silk  and  broadcloth  clothing.  Scraps  and  food 
left  over  from  the  table  are  as  good  quality  as  ever,  and 
should  be  saved  for  the  next  meal. 

212.  Amount  at  a  meal.  —  Rules  prescribing  the  amount 
of  food  to  be  eaten  at  once  cannot  be  given,  any  more 
than  fixed  rules  regulating  the  amount  of  wood  to  be 
added  to  the  fire  in  a  cooking  stove.  Hunger  and  taste 
are  reliable  guides  when  plain  food  is  eaten  slowly. 

213.  Too  much  food.  —  In  some  persons  the  stomach  cannot 
digest  and  absorb  food  so  fast  as  the  lungs  can  furnish  oxygen  for  its 
oxidation.  While  these  persons  eat  heartily  they  generally  remain 
thin,  for,  instead  of  accumulating  food,  they  use  it  up  in  developing 
energy  for  active  work.  They  are  apt  to  overwork  their  stomachs  and  to 
suffer  from  indigestion.  They  need  nutritious  and  easily  digested  food. 
Other  persons  can  digest  food  faster  than  the  lungs  can  supply  oxygen 
for  its  oxidation.  These  persons  eat  little,  but,  since  the  slow  oxidation 
allows  food  to  accumulate,  they  are  apt  to  be  fat  and  lazy  and  to  suffer 
from  lung  troubles.  By  allowing  their  strong  stomachs  to  act  upon  the 
less  easily  digested  foods  their  appetites  will  probably  be  satisfied,  and 
still  not  enough  food  will  be  digested  and  absorbed  to  overtax  their  lungs. 

214.  Starvation.  —  When  man  is  deprived  of  all  food,  life 
is  supported  by  the  oxidation  of  his  own  flesh  as  long  as  it 
lasts.  In  from  six  to  ten  days  a  man  will  lose  two  fifths 
of  his  original  weight,  and  then  death  occurs.  When  water 
is  given,  life  will  last  for  a  much  longer  time. 

215.  Brain  food.  —  Brain  workers  require  the  same  kind  of  food 
as  the  laborer.  In  its  action  the  brain  uses  heat  and  energy,  the  same 
as  any  other  part  of  the  body.  Fish  is  no  more  a  brain  food  than  beef- 
steak. Phosphates,  which  are  popularly  supposed  to  nourish  the  brain, 
are  arrested  at  the  liver ;  but  they  stimulate  the  liver  to  greater  activity, 
so  that  food  is  more  perfectly  assimilated,  and  thus  greater  strength  is 
given  to  the  brain  cells,  as  well  as  to  the  rest  of  the  body.  Phosphorus 
is  found  in  most  foods  in  greater  quantities  than  the  body  needs. 


134  APPLIED   PHYSIOLOGY 

SUMMARY 

1.  About  four  ounces  of  each   of   the  food  elements  — 

albumin,  fat,  and  sugar  —  must  be  eaten  daily. 

2.  To  oxidize  this  amount  of  food  requires  about  twenty- 

four  ounces  of  oxygen,  which  is  about  the  amount 
breathed  in. 

3.  A  diet  of  bread,  eggs,  meat,  milk,  and  butter  will  fur- 

nish the  best  food  elements. 

4.  If  too  much  sugar  or  starch  is  eaten,  the  albumin  and 

fat  are  not  fully  oxidized. 

5.  If  too  much  food  is  eaten,  all  the  oxygen  is  used  up, 

and  there  is  none  left  for  an  extra  exertion. 

6.  If  little  or  no  food  is  eaten,  not  enough  heat  and  energy 

are  produced  to  keep  the  body  alive. 

DEMONSTRATIONS 

59.  Weigh  out  the  different  amounts  of  bread,  eggs,  meat,  milk,  and 
butter  which  are  required  daily.  Also  measure  out  a  quart  of  water. 
This  will  show  the  class  the  amounts  of  food  required  daily. 

60.  Weigh  out  the  required  quantities  of  albumin,  fat,  and  sugar. 
Albumin  may  be  represented  by  gelatine  or  glue. 

REVIEW  TOPICS 

1.  Give  the  amount  of  albumin,  fat,  and  sugar  required 

daily. 

2.  Give  the  amount  of  oxygen  required  to  oxidize  the  food. 

3.  Give  the  results  of  oxidizing  an  excess  of  sugar. 

4.  Give  the  amounts  of  bread,  meat,  etc.,  required  daily  to 

furnish  the  body  with  the  proper  amount  of  albumin, 
fat,  and  sugar. 

5.  Give  the  best  times  for  eating. 

6.  Give  the  effects  of  eating  too  much  food ;  of  too  little. 


CHAPTER   XV 

DRINKING  WATER 

21G.  Pure  water.  —  Water  is  the  only  food  which  man 
habitually  takes  without  its  previous  preparation.  Water 
is  the  same  from  whatever  source,  but  substances  dissolved 
in  the  water  change  its  appearance.  Carbonic  acid  gas, 
oxygen,  and  air  are  dissolved  in  all  ordinary  water,  and  in 
it  float  particles  of  dust  and  harmless  living  germs.  Such 
water  is  clear  and  colorless.  It  has  a  slight  taste,  due  to 
the  dissolved  air.  When  the  air  is  expelled  by  boiling,  the 
water  is  insipid  and  almost  tasteless., 

217.  Hard  and  soft  water.  — Water  also  contains  a  vari- 
able amount  of  mineral  matter,  especially  lime,  soda,  and 
potash.  Water  containing  lime  makes  the  fingers  feel 
slightly  rough  and  puckered.  The  lime  combines  with 
soap,  forming  a  scum  which  will  not  dissolve.  Water  con- 
taining lime  is  said  to  be  hard,  while  water  with  little  or  no 
lime  is  soft.  Although  some  gases  and  minerals  are  dis- 
solved in  all  water,  they  are  harmless  and  do  not  make  it 
impure,  but  rather  they  give  it  a  more  pleasant  taste. 
When  very  hard  water  is  boiled,  some  of  the  lime  is 
deposited  on  the  sides  of  the  kettle,  and  the  water  is 
improved  but  not  made  soft. 

218.  Mineral  waters.  —  When  much  mineral  matter  is  present 
the  water  is  called  mineral  water.  The  principal  minerals  thus  found 
in  water  are  salt,  lime,  soda,  potash,  iron,  and  sulphur.  These  waters 
form  springs  in  various  parts  of  the  country,  and  have  borne  a  great 

135 


136  APPLIED   PHYSIOLOGY 

reputation  as  healing  agents  even  among  the  Indians.  Enormous 
quantities  are  sold  for  drinking  and  medicinal  purposes.  Some  contain 
one  or  two  ounces  of  mineral  substance  to  each  gallon  of  water.  Some 
springs  contain  almost  pure  salt,  and  furnish  the  greater  part  of  the 
table  salt  in  common  use. 

219.  Impure  water.  —  When  water  contains  substances 
which  are  directly  injurious  to  health,  it  is  impure.  Water 
which  stands  in  lead  pipes  may  slowly  dissolve  some  of  the 
lead,  but  if  the  water  is  allowed  to  flow,  the  dissolved  lead 
will  be  washed  away.  Water  from  muddy  or  stagnant 
streams  is  of  a  bitter  taste  and  unpleasant  odor  and  turbid 
in  appearance,  so  that  it  is  not  likely  that  it  should  be  used 
as  a  drink;  but  well  water  often  becomes  polluted  with 
poisons  far  more  injurious  than  those  developed  in  stag- 
nant streams,  and  the  danger  is  all  the  greater  because 
it  often  remains  clear  and  sparkling  and  pleasant  to  the 
taste. 

220.  Decayed  matters  and  disease  germs.  —  The  danger- 
ous substances  most  often  found  in  water  are  decaying 
matter  and  disease  germs.  While  decaying  matter  is 
itself  poisonous,  yet  its  greatest  danger  lies  in  the  fact 
that  it  forms  the  food  upon  which  living  germs  of  disease 
can  live.  These  are  ready  to  grow  when  taken  into  the 
body.  Typhoid  fever  is  almost  always  transmitted  in  this 
way.  In  pure  water  germs  soon  die  of  starvation,  but 
they  grow  readily  if  a  small  amount  of  decaying  matter 
is  present.  Water  which  is  colored  or  has  an  odor  or  a 
taste  is  almost  sure  to  contain  decaying  matter,  which  may 
become  a  breeding  place  for  the  germs.  Such  water 
should  be  avoided;  but  water  which  is  clear  and  sparkling 
may  still  contain  food  for  the  germs. 

221.  Source  of  impurities.  —  Sewage  and  slops  from  a 
person   suffering   with   an   infectious    illness    may   contain 


DRINKING  WATER  1 37 

germs  of  the  disease.  These  germs  may  grow  in  the 
slops  after  they  hav^e  been  emptied.  If  these  slops  find 
their  way  into  a  well,  the  disease  germs  may  continue 
to  grow  and  may  infect  any  one  who  drinks  the  water.  Ice 
from  such  water  may  also  contain  the  germs.  A  shallow 
well  near  any  source  of  dirty  water  may  become  infected 
and  so  be  a  center  for  the  spread  of  disease. 

222.  Purification  by  oxidation  in  the  soil.  —  The  ground 
has  the  power  of  oxidizing  decayed  vegetable  and  animal  matter  so 
that  only  the  mineral  parts  remain.  Slops  from  the  house  are  thus 
oxidized,  if  the  ground  is  not  soaked  through  with  them.  But  when 
the  quantity  is  great,  some  may  work  their  way  through  the  ground  for 
a  considerable  distance  and  finally  enter  the  well. 

223.  Purification  by  filtration.  —  Clean  sand  has  the  power  to 
screen  out  particles  carried  by  the  water.  Screening  out  substances 
from  water  by  passing  it  through  a  powdered  substance  is  called  Ji/^ra- 
tion.  As  the  slops  slowly  soak  through  the  soil,  their  solid  parts  are 
filtered  out  in  the  first  few  inches  of  the  top  soil,  and  if  the  quantity  is 
not  too  great,  are  soon  oxidized.  Soils  differ  in  their  ability  to  filter. 
Clean  sand  is  the  best ;  clay  is  the  poorest.  It  is  almost  impossible  to 
saturate  sandy  soil  about  a  single  house  so  that  decaying  matter  can 
reach  the  wells ;  but  in  villages  and  cities  the  soil  is  so  completely 
soaked  that  the  well  water  of  these  places  is  impure ;  and  at  any  time 
germs  may  enter  the  polluted  wells  and  grow. 

224.  Purification  by  running  water.  —  The  third  way  in 
which  water  is  purified  is  by  the  action  of  the  air  and  sun  upon  running 
water.  Sewage  from  the  towns  is  conducted  into  rivers,  and  the  sun- 
light and  agitation  of  the  waters  soon  cause  the  waste  matters  and 
germs  to  be  oxidized. 

225.  Purification  by  boiling.  —  It  is  dangerous  to  use 
impure  water  for  washing,  for  germs  may  remain  upon 
the  things  washed.  Typhoid  fever  has  been  spread  by 
milk  cans  which  were  washed  in  water  from  a  polluted 
well.  A  ready  safeguard  against  the  greater  dangers  of  im- 
pure water  is  boiling,  which  destroys  the  germs  of  disease. 


138  APPLIED    PHYSIOLOGY 


SUMMARY 

1.  Water  containing  lime  is  hard,  but  without  lime  it  is 

soft.     Lime  seldom  injures  water  for  drinking  pur- 
poses. 

2.  When  other  minerals,  such  as  sulphur,  iron,  soda,  or 

potash,  are  present,  water  is  called  mineral  water. 
Such  water  is  used  as  medicine. 

3.  Air  dissolved  in  water  gives  it  a  pleasant  taste. 

4.  Water  containing  decaying  matter  is  poisonous. 

5.  The   greatest  danger  from   impure  water   lies   in  the 

germs  of  disease  which  it  may  contain. 

6.  Boiling  the  water  is  the  best  safeguard  against  impure 

water. 

7.  The  soil  purifies  water  by  oxidizing  and  filtering  the 

impurities.     Running  water  is  generally  pure. 

DEMONSTRATIONS 

61.  Show  that  all  water  contains  mineral  matter  by  evaporating  a 
few  drops  of  pure  spring  water  upon  a  piece  of  clean  glass.  A  little 
white  spot  will  be  left  by  each  drop.  Boil  some  water  and  notice  the 
absence  of  taste.  Cool  it  and  shake  it  in  a  can,  and  notice  its  natural 
taste  again.  Set  aside  some  pure  water  containing  a  few  bread  crumbs 
or  a  shred  of  meat,  and  notice  the  unpleasant  odor  of  decay  developed 
in  a  few  days. 

62.  A  rough  test  for  the  purity  of  water  is  to  stir  in  a  Httle  pure 
sugar  and  set  it  aside.  If  it  contains  any  organic  matter,  it  will  turn 
yellowish  in  a  few  days,  but  otherwise  it  will  remain  colorless.  Collect 
some  rain  water  from  a  dirty  building,  or  mud-puddle  water,  or  water 
from  a  barnyard  well,  and  note  the  color  and  the  odor.  After  keeping 
it  a  few  days,  note  the  deepened  color  and  worse  odors,  showing  decay 
within  the  water. 

63.  Doubtless  the  class  will  ask  to  be  shown  ''animalculae"  in 
water.  Water  has  to  be  almost  turbid  and  putrid  before  living  beings 
are  present  in  sufficient  numbers  to  be  easily  detected  with  a  micro- 


•       DRINKING   WATER  1 39 

scope.  If  a  drop  of  very  stagnant  water  is  examined  under  the  micro- 
scope with  a  power  of  100  to  400  diameters,  many  strange  beings  will 
be  seen  moving  about.  Place  a  little  hay  in  a  bottle  of  water  and  exam- 
ine a  drop  of  the  water  every  day,  and  notice  the  changing  forms  of  the 
living  beings  as  one  kind  dies  and  another  is  produced. 

REVIEW  TOPICS 

1.  Describe  the  appearance  and  taste  of  pure  water. 

2.  State  what  substances  are  found  in  all  water ;  what  in 

mineral  v/ater ;  and  the  difference  between  Jiard  and 
jd?// water. 

3.  State  the  two  common  dangerous  impurities  of  water. 

4.  Give  three  ways  in  which  nature  purifies  water. 

5.  Show  how  to  avoid  pollution  of  a  well. 

6.  Show  how  to  render  impure  water  safe  for  use. 


CHAPTER   XVI 
NARCOTICS 

226.  What  man  eats  besides  food.  —  Besides  eating  food 
and  harmless  things  which  please  the  taste,  man  also  eats 
a  variety  of  dangerous  substances,  both  for  pleasure  and 
to  overcome  some  real  or  fancied  weakness  of  the  body. 
The  physician  prescribes  them  to  overcome  diseases  of 
the  cells,  but  thoughtless  and  ignorant  people  use  them  on 
their  own  responsibility,  and  suffer  great  harm  thereby. 
They  may  be  divided  into  narcotics,  drugs,  2c^A  poisons. 

227.  Narcotics.  —  There  is  a  class  of  drugs  which  be- 
numb the  sense  of  pain  and  fatigue  and  lessen  the  action 
and  strength  of  the  cells  of  the  body.  These  drugs  are 
called  narcotics.  They  all  are  powerful  poisons.  They 
lessen  the  sense  of  effort  and  of  fatigue,  and  are  often 
supposed  to  be  stimulants.  A  peculiarity  common  to  all 
is,  that  when  their  benumbing  effects  have  passed  off,  the 
real  weakness  of  the  body  becomes  doubly  apparent,  and 
there  is  an  overwhelming  desire  for  more  of  the  drug  to 
benumb  the  increased  weakness  caused  by  the  first  dose. 
Thus  enslaving  habits  are  formed. 

228.  Alcohol  as  a  narcotic.  —  Alcohol  should  he  classed  as 
a  narcotic  drug.  It  really  belongs  to  the  class  of  stimulants  as  well. 
A  small  amount  acts  as  a  stimulant ;  but  a  large  amount  overwhelms 
the  body  and  produces  an  insensibility  to  pain  and  fatigue,  a  dullness  of 
mind,  and  a  deep  sleep.  The  use  of  alcohol  tends  to  become  a  fixed 
habit,  as  is  the  case  with  other  narcotics. 

140 


NARCOTICS  141 

229.  Alcoholic  poisoning.  —  Besides  slow  poisoning,  alco- 
hol can  produce  severe  poisonous  effects  at  once.  A  man 
^'  dead  drunk"  is  poisoned  by  alcohol,  and  is  in  danger  of 
his  life.  In  treating  him,  vomiting  should  be  induced  as 
soon  as  possible.  He  should  be  rubbed  to  keep  up  the 
circulation,  and  ■  stimulated  with  hot  coffee.  Keep  his 
body,  and  especially  his  feet,  warm. 

230.  Tobacco  and  nicotine.  —  The  essential  part  of  tobacco 
is  a  strong  narcotic  poison  called  iiicotine.  Pure  nicotine 
is  a  clear  and  colorless  liquid.  It  can  be  turned  to  vapor, 
and  is  found  in  the  smoke  when  the  tobacco  is  burned.  It 
is  a  powerful  poison,  producing  stomach  sickness  and  great 
weakness  of  all  the  cells  of  the  body,  especially  of  the 
heart.     Two  or  three  drops  will  kill  a  man. 

231.  Effects  of  its  continuous  use. — When  used  continu- 
ously, the  body  becomes  somewhat  accustomed  to  nicotine, 
so  that  it  does  not  produce  so  great  a  feeling  of  sickness. 
Then  instead  of  producing  a  feeling  of  weakness,  it  acts 
more  to  benumb  the  cells  and  to  quiet  the  body.  This  is 
really  the  first  stage  of  poisoning,  although  it  seem.s  like  a 
stimulation.  If  a  little  more  tobacco  than  usual  is  used, 
the  benumbed  and  pleasant  feeling  changes  to  one  of  sick- 
ness, as  though  it  were  being  used  for  the  first  time.  It 
always  continues  to  have  bad  effects  upon  the  muscles, 
heart,  lungs,  eyes,  and  brain.  Tobacco  is  especially  inju- 
rious to  young  persons,  hindering  their  growth  and  lessen- 
ing their  strength. 

232.  How  tobacco  is  used.  —  Tobacco  is  used  in  smoking, 
in  chewing,  and  in  snuffing  it  up  the  nose. 

233.  Smoking.  —  Tobacco  is  smoked  in  a  pipe  or  by 
lighting  the  end  of  a  roll  called  a  cigar.  Some  of  the 
nicotine  is  turned  to  vapor  and  enters  the  mouth,  where 
it  may  be  absorbed.     Some  of  the  nicotine  is  half  burned, 


142  APPLIED   PHYSIOLOGY 

and  forms  a  substance  called  pyridine^  which  is  even  more 
poisonous  than  nicotine.  In  a  cigar  the  burning  is  more 
complete,  and  less  pyridine  is  formed.  Cigarettes  are  small 
cigars  made  of  shredded  tobacco.  They  are  cheap  and 
may  be  quickly  smoked,  and  are  less  liable  to  produce  imme- 
diate sickness  than  a  cigar.  So  the  young  are  especially 
apt  to  use  them.  But  they  are  commonly  used  to  excess, 
and  so  make  up  in  quantity  of  poison  what  they  lack  in 
quality. 

234.  Chewing.  —  Chewing  tobacco  is  the  most  harmful 
form  of  its  use,  for  all  the  nicotine  is  taken  into  the  mouth. 
Few  people  can  chew  tobacco  without  spitting  out  the 
saliva  which  contains  the  nicotine.  The  continuous  spit- 
ting which  is  necessary  to  get  rid  of  the  saliva  makes  this 
form  of  using  tobacco  offensive  to  everybody  near  the 
chewer.  This  reason  alone  should  deter  any  one  from  the 
practice  of  chewing  tobacco. 

235.  Snuff.  —  Snuff  is  powdered  tobacco.  A  hundred 
years  ago  it  was  fashionable  for  women,  as  well  as  men, 
to  use  snuff.     Now  a  snuffbox  is  a  rare  curiosity. 

236.  Adulteration  of  tobacco.  — The  nicotine  from  stalks  and 
remnants  is  extracted  by  boiling,  and  the  liquor  is  used  to  saturate  poor 
tobacco  and  the  leaves  of  other  plants. 

Chewing  tobacco  owes  much  of  its  taste  to  rum,  molasses,  licorice, 
and  other  things  with  which  it  is  flavored. 

Most  cigarettes  are  flavored  with  drugs  which  color  the  fingers  of 
the  smokers.  Cigarettes  are  harmful  enough  at  best,  but  the  harm  is 
far  greater  when  they  contain  opium.  Probably  a  great  part  of  the 
craving  which  cigarettes  induce  is  caused  by  the  opium. 

237.  Tobacco  habit.  —  Like  all  other  narcotics,  when  it 
is  used  for  a  short  time  tobacco  produces  a  persistent  crav- 
ing. Men  laugh  at  the  idea  of  being  slaves  to  such  a 
small  thing  as  smoking  or  chewing,  and  yet  when  the  habit 


NARCOTICS  143 

is   interrupted,   there   follows   a   peculiar   unsatisfied  and 
nervous  feeling  which  few  men  are  able  to  overcome. 

Alcohol  and  tobacco  often  go  hand  in  hand.  Tobacco  produces  a 
dry  state  of  the  mouth  which  demands  drink,  while  alcohol  causes  a 
nervous  excitement  which  the  benumbing  tobacco  tends  to  overcome. 
Most  users  of  alcohol  smoke.  The  only  way  to  break  off  the  habit  of 
using  tobacco  is  to  do  so  by  resolute  efforts  of  the  will.  So-called  cures 
of  the  habit  are  of  no  value,  for  they  cannot  give  a  man  a  strong  will. 
On  the  other  hand,  they  may  induce  sickness. 

238.  Tobacco  poisoning.  —  Severe  tobacco  poisoning  is 
rare ;  for  when  swallowed  or  inhaled,  it  produces  vomiting, 
which  expels  the  poison.  When  applied  to  the  skin  in  the 
form  of  a  poultice,  as  is  sometimes  done,  enough  may  be 
absorbed  to  produce  great  weakness,  for  then  the  stomach 
cannot  expel  it.  The  principal  sign  of  poisoning  is  extreme 
weakness  of  the  muscles  and  heart. 

To  treat  it,  strong  coffee  should  be  given,  and  the  patient 
should  be  kept  perfectly  at  rest. 

239.  Opium.  —  Opium  is  a  narcotic  drug  which  is  used 
to  benumb  the  feelings  of  fatigue  and  care.  A  little  of  the 
drug  acts  partly  as  a  real  stimulant,  causing  the  cells  to 
act  more  vigorously  and  clearly.  At  the  same  time  its 
benumbing  action  is  beginning,  and  only  a  little  more  is 
needed  to  produce  a  drowsy  feeling  or  a  deep  sleep.  Just 
as  it  causes  the  brain  cells  to  cease  acting  in  sleep,  so  also 
it  lessens  the  action  of  all  the  other  cells,  and  especially 
of  those  of  the  alimentary  canal.  The  disturbance  in  the 
action  of  the  intestine  sets  up  digestive  trouble,  which 
extends  rapidly  to  the  liver.  Then  the  nutrition  of  the 
whole  body  is  lowered.  No  habit  is  more  enslaving  or 
more  harmful  in  its  effects. 

240.  Cure  of  the  opium  habit.  —  The  only  cure  for  the 
opium  habit,  and  yet  a  safe  and  sure  one,  is  to  keep  the 


144  APPLIED   PHYSIOLOGY 

patient  entirely  away  from  the  drug  for  a  few  weeks,  con- 
fining him  if  necessary.  After  a  short  time  the  craving 
disappears  and  the  patient  recovers  his  health. 

241.  Opium  poisoning.  —  A  lump  of  opium  the  size  of  a 
small  pea,  and  weighing  about  two  grains,  is  enough  to  put 
a  man  into  a  deep  sleep.  Twice  that  amount  may  cause 
death.  When  a  person  takes  an  overdose  he  falls  into  a 
deep  sleep,  from  which  he  can  be  awakened  only  with 
difficulty.  He  breathes  very  slowly,  and  distends  the 
lungs  very  slightly.  The  pupils  of  his  eyes  contract  to 
small  points.  These  three  signs  nearly  always  mean 
opium  poisoning.  They  should  be  remembered,  for  this 
is  the  most  common  form  of  poisoning. 

242.  Treatment  of  opium  poisoning.  —  First.  Keep  the 
patient  awake  by  such  vigorous  measures  as  slapping  his 
face,  shaking  his  body,  and  compelling  him  to  walk. 

Second.  Induce  vomiting.  A  tablespoonful  of  mustard 
in  water  should  be  given  at  once  if  the  person  can  swallow. 
Tickling  the  throat  with  the  finger  or  a  feather  will  gener- 
ally cause  vomiting. 

Third.  Stimulate  the  patient  with  strong,  hot  coffee. 
Carry  out  these  measures  slowly  and  deliberately. 

243.  Forms  of  opium.  —  Opium  is  the  dried  juice  of  a  kind  of 
poppy  plant  growing  in  Southern  Asia.  Laudamun  is  opium  dissolved 
in  ten  parts  of  alcohol.  Paregoric  is  a  more  dilute  solution  of  opium. 
A  teaspoonful  of  it  contains  one  quarter  of  a  grain  of  opium.  About 
one  tenth  of  opium  is  a  white  substance  called  7norphine.  One  quarter 
of  a  grain  of  morphine  will  cause  a  deep  sleep  and  contracted  pupils 
like  a  large  dose  of  opium. 

244.  Use  of  opium.  —  Opium  is  used  to  quiet  pain,  pro- 
duce sleep,  and  to  quiet  the  intestine. 

Paregoric  is  sometimes  used  to  quiet  babies  when  they 
cry.     It  produces  indigestion  and  leaves  the  child  worse 


NARCOTICS  145 

than  before.     **  Soothing  sirups  "  are  nearly  always  some 
preparation  of  opium. 

245.  Chloral,  —  Chloral  is  a  colorless  solid,  having  a 
peppery  odor  and  taste.  About  twenty  grains  will  produce 
sleep,  but  an  overdose  may  produce  death.  It  injures  the 
digestive  organs  and  weakens  the  whole  body.  It  is  a 
narcotic  and  a  poison. 

246.  Chloral  poisoning.  —  In  treating  a  case  of  chloral 
poisoning  the  patient  should  be  kept  awake  by  walking 
him  about,  or  even  by  slapping  him.  Give  a  tablespoon- 
ful  of  mustard  in  water  to  make  him  vomit.  Then  give 
strong  coffee  to  stimulate  him. 

247.  Cocaine.  —  Cocaine  is  a  drug  which,  when  injected 
under  the  skin  or  applied  to  a  mucous  membrane,  takes 
away  the  sense  of  feeling  of  the  part.  A  grain  of  it  will 
render  a  large  area  so  completely  insensitive  for  half  an 
hour  that  large  operations  can  be  performed  without  sense 
of  pain.  It  may  cause  excitement  like  the  beginning  of 
a  state  of  drunkenness  ;  sometimes  it  produces  great  weak- 
ness of  the  heart  and  death. 

The  excitement  caused  by  the  drug  is  pleasant,  and  per- 
sons can  acquire  a  slavish  habit  of  its  use.  It  rapidly  dis- 
turbs digestion  and  nutrition,  and  soon  causes  death.  It 
is  one  of  the  most  rapid  and  terrible  forms  of  habitual  drug- 
taking. 

248.  Hasheesh.  —  Hasheesh  is  the  juice  of  the  Indian 
hemp  plant,  and  is  sold  as  a  medicine  under  the  name  of 
cannabis  indica.  In  Southern  Asia  it  is  extensively  used 
as  a  narcotic.  It  produces  a  happy  delirium,  in  which 
a  person  sees  most  beautiful  persons  and  figures.  The 
state  is  really  a  temporary  insanity,  in  which  one  is  liable 
to  injure  others.  The  word  "assassin"  means  one  under 
the  influence  of  hasheesh. 

OV.  PHYSIOL.  —  10 


146  APPLIED   PHYSIOLOGY 

249.  Chloroform.  —  Chloroform  is  a  sweet-smelling  liquid 
which,  when  breathed  into  the  lungs,  causes  a  deep  sleep. 
It  is  used  to  produce  insensibility  during  surgical  opera- 
tions. Its  use  requires  extreme  care,  for  it  can  easily 
result  in  death.  No  one  should  even  smell  a  bottle  con- 
taining it,  for  two  or  three  breaths  of  it  may  render  a  per- 
son insensible. 

SUMMARY 

1.  Narcotics  lessen  the  sense  of   fatigue  and  pain  and 

produce  sleep,  but  weaken  the  body  and  may  cause 
death.  Their  use  may  become  an  uncontrollable 
habit. 

2.  Alcohol  is  a  kind  of  narcotic. 

3.  Tobacco  contains  the  narcotic  fiicotine.     A  little  nico- 

tine quiets  the  cells,  while  more  causes  weakness, 
and  stomach  sickness  which  may  result  in  death. 

4.  Tobacco  used  in  any  form  produces  poisonous  effects. 

5.  The  tobacco  habit  tends  to  the  use  of  strong  drink. 

6.  Opium  quiets  the  cells  of  the  body,  lessens  the  sense 

of  pain,  and  produces  sleep.  A  little  causes  a  feeling 
of  exhilaration,  while  a  few  grains  may  cause  death. 

7.  The  opium  habit  deranges  digestion  and  finally  causes 

death. 

8.  In    poisoning  by  opium  there  are  a  deep  sleep  and 

contracted  pupils  and  slow  breathing. 

9.  The  poisoned  person  should  be  kept  awake,  made  to 

vomit,  and  stimulated  by  coffee. 

10.  Laudanum,    paregoric,    and    soothing    sirups    are    all 

forms  of  opium. 

11.  Chloral   produces   sleep.     A   large   dose   may   cause 

death.     Treat  its  poisoning  like  opium  poisoning. 

12.  Chloroform,  when  inhaled,  produces  insensibility. 


NARCOTICS  147 

REVIEW  TOPICS 

1.  Define  and  describe  narcotics  and  show  how  their  use 

may  become  a  habit. 

2.  Show  that  alcohol  is  a  narcotic,  and   give  the  signs 

and  treatment  of  its  poisonous  effects. 

3.  Describe  the  poison  of  tobacco  and  its  effects. 

4.  Describe  the  harm  resulting  from  the  use  of  the  several 

forms  of  tobacco. 

5.  Show  the  fraud  and  harm  of  adulterating  tobacco. 

6.  Show  that  the  use  of  tobacco  and  alcohol  naturally  go 

together. 

7.  Describe  the  effects  of  opium  and  the  opium  habit. 

8.  Describe  the  signs  and  treatment  of  opium  poisoning. 

9.  Name  some  common  forms  of  opium  and  give  their 

uses. 

10.  Describe  chloral,  and  give  the  signs  and  treatment  of 

poisoning  by  it. 

11.  Describe  cocaitie,  its  use  in  surgery,  and  its  poisonous 

effects. 

12.  Describe  hasheesh. 

13.  Describe  chloroforvi  and  the  danger  of  its  use. 


CHAPTER   XVII 
DRUGS   AND  POISONS 

250.  Nature  of  disease.  —  Disease  is  due  to  some  de- 
rangement of  the  action  of  the  cells  of  the  body.  The 
derangement  is  almost  always  produced  by  overwork  of 
some  kind,  for  the  cells  are  able  to  protect  the  body 
against  all  ordinary  causes  of  disease.  Few  people  who 
are  exposed  to  epidemic  diseases  take  them,  because  the 
cells  are  able  to  destroy  the  germs  as  fast  as  they  enter 
the  body.  If  men  would  eat,  breathe,  and  in  all  things 
live  as  physiology  and  hygiene  show  that  nature  intended 
them  to  live,  the  cells  would  be  strong  enough  to  resist 
almost  any  disease. 

261.  Action  of  drugs.  —  Each  drug  has  a  special  influ- 
ence upon  certain  cells  of  the  body,  and  is  able  either  to 
stimulate  or  to  restrain  their  action.  Under  the  influence 
of  the  proper  drug,  each  deranged  cell  takes  in  nourishment 
and  performs  its  duties  more  perfectly,  and  soon  overcomes 
the  sickness.  Thus  the  cells  themselves,  and  not  the  drug, 
cure  the  disease. 

252.  Action  of  a  few  common  drugs. — When  the  liver  is 
deran<^ecl,  calomel  or  podophyllin  will  usually  stimulate  it  to  action.  In 
stomach  indigestion  inuriatic  acid  and  pepsin  supply  the  missing  diges- 
tive agents.  When  the  heart  is  weak,  digitalis  or  strychnine  cause  it 
to  act  more  strongly,  while  if  it  is  excited,  aconite  will  quiet  it.  A  fever 
is  often  lowered  by  aconite  or  phenacetine.  When  there  is  pain,  opium 
will  generally  relieve  it.     When  the  brain  is  excited  and  the  person  is 

148 


DRUGS   AND   POISONS  I49 

nervous  or  delirious,  chloral  or  bromide  of  potash  will  quiet  the  cells. 
These  are  a  few  examples  of  the  actions  of  drugs  which  physicians 
prescribe. 

253.  Quack  medicines.  —  Drugs  should  never  be  given  except 
by  a  physician.  The  country  is  flooded  with  medicines  advertised  to 
cure  various  diseases.  People  who  take  them  generally  get  well,  but 
they  forget  that  the  cells  of  the  body  themselves  tend  to  overcome  all 
diseases,  and  that  in  all  probability  they  had  no  disease  at  all,  but  were 
only  feeling  bad  because  of  improper  eating,  or  of  overwork. 

254.  Poisons.  —  All  narcotics  and  drugs  are  poisons  and 
cause  sickness  or  death  when  taken  in  overdoses.  The 
signs  of  poisoning  are  much  alike  in  all  cases.  A  person 
previously  well  suddenly  feels  very  sick  and  weak,  or  be- 
comes unconscious.  Vomiting  often  occurs,  and  pain  is 
often  present. 

255.  Treatment  of  poisoning. — The  first  thing  to  do 
whenever  a  poison  is  swallowed  is  to  empty  the  stomach 
as  quickly  as  possible.  Almost  anybody  can  be  made  to 
vomit  by  tickling  the  throat  with  a  finger,  or  with  a  feather 
passed  through  the  nose  if  the  mouth  cannot  be  opened. 
A  tablespoonful  of  mustard  in  a  cup  of  warm  water  will 
generally  cause  vomiting  and  is  always  safe.  A  teaspoon- 
ful  of  alum  in  water  will  act  in  the  same  way.  Water  or 
soft  food  of  any  kind  should  then  be  swallowed  and  vomit- 
ing continued,  so  as  to  remove  all  traces  of  the  poison. 

The  second  thing  is  to  give  castor  oil  or  salts,  so  as  to 
remove  any  poison  which  may  have  entered  the  intestine. 

The  third  thing  is  to  give  something,  called  an  antidote^ 
which  will  destroy  the  poison  in  the  body. 

The  fourth  thing  is  to  give  a  stimulant,  for  the  person 
will  be  very  weak.  Strong  coffee  should  be  given  by  the 
cupful,  without  sugar  or  milk. 

256.  Poisoning  by  acids  or  alkalies.  —  If  the  lips  and 
mouth  are  covered  with   a  white  film   or  are  raw,  some 


I50  APPLIED   PHYSIOLOGY 

acid  or  alkali  has  probably  been  swallowed.  If  it  is  an 
alkali,  a  drink  of  weak  vinegar  should  be  given  at  once  as 
an  antidote.  If  it  is  an  acid,  soda,  soapsuds,  or  limewater 
should  be  given  as  an  antidote. 

Also  give  water,  or  flour  and  water,  or  the  white  of  an 
^ZZ^  o^  milk,  so  as  to  dilute  the  substance  as  soon  as 
possible. 

257.  Carbolic  acid.  —  When  swallowed,  pure  carbolic 
acid  produces  great  weakness  and  rapid  death.  In  small 
doses,  or  even  applied  to  the  skin  in  surgical  dressings,  it 
may  produce  headache  and  weakness,  which  may  result  in 
death. 

In  treating  its  poisonous  effects,  a  stomach  pump  will 
generally  have  to  be  used  to  remove  the  poison,  because 
the  stomach  will  be  paralyzed  by  the  burning  to  which  it 
is  subjected.     The  antidote  is  Epsom  salts. 

258.  Narcotic  poisoning.  —  If  the  person  poisoned  is 
sleepy,  it  shows  that  a  narcotic  like  opium  or  chloral  has 
been  taken.  Care  should  be  taken  not  to  mistake  a  faint- 
ing spell  for  the  drowsiness  of  poisoning.  In  faintness, 
the  face  is  of  a  deathly  pale  color,  and  no  pulse  can  be 
felt,  and  breathing  ceases,  while  in  drowsiness  the  face  is 
of  a  natural  or  even  deeper  red  color,  the  pulse  can  be 
felt,  and  breathing  will  continue. 

259.  Strychnine  poisoning.  —  Strychnine  produces  vio- 
lent convulsions,  like  lockjaw,  within  half  an  hour  after  it 
has  been  taken.  Vomiting  should  be  induced  at  once. 
Chloral  and  bromide  of  potash  are  its  antidotes,  and 
should  be  given  as  soon  as  possible,  to  quiet  the  convul- 
sions.    In  an  emergency  tobacco  may  be  used. 

260.  Arsenic  and  other  metals.  —  Rat  poison  and  Paris 
green  contain  arsenic.  Arsenic  is  a  metal,  and  its  poison- 
ing is  much  like  poisoning  by  mercury,  lead,  copper,  silver^ 


DRUGS   AND   POISONS  151 

or  antimony.  Sttgar  of  lead  and  white  lead  paint  are  the 
common  forms  of  lead  which  poison  the  body.  Copper 
is  seldom  dangerous.  Some  forms  of  silver  are  very 
poisonous. 

Antimony  is  poisonous  in  the  form  of  tartar  e7netic  and 
wine  of  antimony^  both  of  which  are  used  in  treating  colds. 

All  forms  of  metallic  poisoning  are  much  alike.  Vomit- 
ing usually  comes  on  within  half  an  hour,  followed  by 
great  weakness,  cramps  in  the  abdomen,  and  burning  thirst. 
If  vomiting  has  not  freely  occurred,  it  should  be  induced 
by  tickling  the  throat  or  by  giving  mustard  in  water. 

Afterwards  the  white  of  eggs,  flour  paste,  or  milk  should  be  given  as 
an  antidote.  The  albumin  of  these  substances  forms  a  chemical  union 
with  the  metal,  producing  a  harmless  compound  which  should  be 
vomited  and  more  of  the  antidote  given. 

The  special  antidote  for  arsenic  is  oxide  of  ir 071.  The  settlings  which 
form  in  a  mixture  of  tincture  of  iron  and  baking  soda  may  be  used  in  an 
emergency.  The  special  antidote  for  lead  is  Epsom  salts;  for  silver, 
common  salt ;  and  for  antimony,  ta?i7iin,  which  is  found  in  a  strong  tea 
made  of  almost  any  bark. 

261.  Phosphorus.  —  Phosphorus  poisoning  may  occur 
from  sucking  the  ends  of  matches.  It  produces  vomiting 
and  violent  cramps  in  the  abdomen  for  two  or  three  days, 
and  then  jaundice  appears,  with  delirium  and  death.  It 
resembles  a  slow  poisoning  by  a  metal. 

Phosphorus  poisoning  is  treated  by  giving  something  to  cause  vomit- 
ing and  to  expel  the  poison  from  the  intestine.  Always  avoid  castor 
oil  or  other  fat,  for  phosphorus  is  dissolved  by  fat.  A  small  pinch  of 
sulphate  of  copper  (blue  vitriol)  given  every  few  minutes  will  destroy 
the  poison  and  also  cause  vomiting. 

262.  Aconite.  —  Aconite  produces  extreme  weakness  of 
the  whole  body.  A  tingling  in  the  throat  is  the  only  dis- 
tinguishing sign  of  the  poison. 


152  APPLIED    PHYSIOLOGY 

A  poisoned  person  should  be  kept  absolutely  quiet,  and 
strong  coffee  should  be  given  as  a  stimulant. 

263.  Belladonna.  —  Belladonna,  or  its  active  principle, 
atropine,  is  used  to  enlarge  the  pupil  in  examinations  of 
the  eye.  In  overdoses  it  produces  redness  of  the  face, 
dryness  of  the  throat,  enlargement  of  the  pupil  of  the  eye, 
delirium,  and  great  weakness.  The  enlarged  pupil  is  its 
distinguishing  sign.  Its  treatment  consists  in  giving  an 
emetic,  stimulating  by  coffee,  and  giving  tannin  or  strong 
bark  tea. 

264.  Mushroom  poisoning.  —  Poisonous  mushrooms  pro- 
duce violent  cramps  in  the  abdomen,  with  vomiting  and 
great  weakness.  One  form  produces  symptoms  within  an 
hour  or  two,  and  is  seldom  fatal,  for  the  poison  is  thrown 
off.  The  other,  and  by  far  the  more  dangerous,  form  of 
poisoning  does  not  come  on  for  ten  or  twelve  hours,  or 
until  the  poison  has  entered  the  intestine.  In  poisoning 
by  mushrooms,  vomiting  should  be  induced,  and  castor  oil 
given  to  remove  the  poison  from  the  intestine.  Strong 
coffee  should  be  given  as  a  stimulant. 

265.  Decayed  food.  —  All  forms  of  decayed  food,  espe- 
cially fish,  eels,  and  crabs,  may  produce  vomiting,  cramps, 
and  weakness,  like  mushroom  poisoning.  The  symptoms 
usually  come  on  within  six  hours  after  eating,  and  are  seldom 
fatal.    The  treatment  is  to  empty  the  stomach  and  intestine. 

266.  Alkaloids.  —  The  active  principles  of  many  vege- 
table drugs  can  be  separated  from  the  crude  drugs.  They 
are  called  alkaloids.  Nicotine,  morphine,  strychnine,  atro- 
pine, and  quinine  are  alkaloids.  Over  one  hundred  in  all 
are  known.  A  single  grain  of  almost  any  alkaloid  except 
quinine  can  produce  violent  poisoning. 

267.  Leucomaines.  —  As  a  result  of  the  imperfect  oxida- 
tion of  albumin  within  the  body,  compounds  resembling 


DRUGS   AND   POISONS  1 53 

alkaloids  are  formed.  They  are  called  leiicomaines.  They 
circulate  in  the  blood  and  produce  headaches,  drowsiness, 
and  other  mild  forms  of  poisoning  which  may  become 
severe  and  produce  death  when,  as  in  Bright's  disease, 
the  kidneys  and  skin  do  not  remove  the  poisons.  At  least 
sixteen  leucomaines  are  known. 

268.  Ptomaines.  —  As  a  result  of  decay  and  other  changes 
after  death,  another  set  of  poisons  like  alkaloids  and  leuco- 
maines are  produced.  They  are  called  ptomaines.  They 
cause  most  of  the  symptoms  produced  by  eating  decayed 
meat.  A  special  kind  of  the  poison,  called  tyrotoxicon^ 
sometimes  forms  in  milk  and  ice  cream  which  has  been 
kept  for  some  time.  Ptomaines  and  leucomaines  can 
always  be  found  in  the  bodies  of  dead  persons. 

269.  Hypodermic  injections.  —  When  injected  beneath  the 
skin  by  means  of  a  hypodermic  needle,  drugs  and  poisons  reach  the 
blood  at  once  and  produce  much  more  powerful  and  rapid  results  than 
when  absorbed  from  the  stomach.     Alkaloids  are  well  fitted  for  this  use. 

270.  Snake  bites.  —  In  the  upper  jaw  of  a  poisonous 
snake  is  a  sharp,  hollow  tooth,  which  is  the  outlet  for 
a  bag  of  poison.  When  the  snake  bites,  the  pressure  of 
the  flesh  against  the  bag  forces  some  poison  through 
the  tooth,  which  thus  acts  as  a  hypodermic  needle.  The 
poison  is  a  kind  of  leucomaine.  It  produces  pain  and 
swelling  at  the  point  of  injection,  great  weakness  of  the 
whole  body,  and  sometimes  death. 

The  treatment  of  snake  bites  must  be  prompt.  A 
handkerchief  should  be  tied  very  tightly  round  the  limb, 
above  the  wound,  so  as  to  prevent  the  poison  from  reach- 
ing the  whole  body.  Then  the  wound  should  be  sucked 
for  some  time,  so  as  to  remove  as  much  as  possible  of  the 
poison.  No  harm  can  come  to  the  person  who  sucks  the 
wound  if  the  blood  is  spit  out  at  once.     If  bleeding  does 


154  APPLIED    PHYSIOLOGY 

not  take  place  freely,  the  wound  should  be  cut  open. 
Active  stimulation  with  such  substances -as  strong  coffee 
or  ammonia  is  also  necessary. 

271.  Insect  stings  and  bites.  —  Bees,  wasps,  and  hornets  pos- 
sess a  hollow  sting  through  which  the  insect  injects  poison  into  the  flesh. 
This  poison  produces  swelling  and  pain,  and  if  there  are  a  great  num- 
ber of  stings,  there  will  also  be  a  considerable  weakness  of  the  whole 
body.  Usually  the  swelling  begins  to  decrease  within  an  hour.  To 
allay  the  smarting,  a  lump  of  cold  mud  is  an  effective  remedy.  Carbolic 
acid  in  water  sopped  on  with  a  cloth  is  also  good.  If  the  insect  has 
left  its  sting  in  the  flesh,  it  should  be  removed  by  pressing  over  the 
sting  with  the  open  end  of  a  watch  key,  or  by  picking  it  out  with  the 
point  of  a  sharp  knife. 

The  bites  of  mosquitoes  and  of  flies  produce  swelling  and  pain  or 
itching  in  some  people.  Ammonia  water  or  carbolic  acid  in  water 
usually  gives  relief. 

SUMMARY 

1.  Disease  is  a  derangement  in  the  action  of  some  of  the 

cells  of  the  body.     Drugs  either  stimulate  or  retard 
the  action  of  the  cells. 

2.  All  narcotics  and  drugs  are  poisons. 

3.  In  every  case  of  poisoning  the  stomach  and  intestine 

should  be   emptied   at   once,  and    a   stimulant  with 
•an  aiitidote  to  destroy  the  poison  should  be  given. 

4.  Spoiled  or  poisonous  food  produces  stomach  and  intes- 

tinal disturbance.       It  should  be  expelled  from  the 
body  as  soon  as  possible. 

5.  The   active    principles  of   many   vegetable    drugs    are 

called  alkaloids. 

6.  Leucomaines  and  ptomaines  are  substances  resembling 

alkaloids,  but  are  produced  in  the  bodies  of  animals. 

7.  The    poisons    of    snakes    and    insects    are    substances 

like  leucomaines,  and  are  injected  into  the  flesh  by 
means  of  a  hollow  tooth  or  sting. 


DRUGS  AND   POISONS  1 55 

REVIEW  TOPICS 

1.  Describe  the  nature  of  disease  and  how  drugs  tend  to 

restore  health. 

2.  Describe  the  general  signs  and  treatment  oi  poisoning. 

3.  Describe  the  treatment  of  poisoning  by  acids ,  and  by 

alkalies. 

4.  Describe  carbolic  acid  poisoning  and  its  treatment. 

5.  Distinguish  between  the   drowsiness  due  to  narcotic 

poisoning  and  a  fainting  spell. 

6.  Describe  strychnine  poisoning  and  its  treatment. 

7.  Describe  poisoning  by  arsejiic  and  give  its  treatment. 

8.  Give  the  signs  and  treatment  of  poisoning  by  metals 

in  general. 

9.  Describe   phosphorits   poisoning    and    give    its   treat- 

ment. 

10.  Describe  poisoning  by  aconite ;  by  belladonna. 

1 1 .  Describe    poisoning   by  mushrooms,  and   by  decayed 

food. 

12.  Describe  alkaloids,  lenco^naines,  ptomaines ^  and  their 

poisonous  effects. 

13.  Describe  hypodermic  injections. 

14.  Describe  S7iake  and  i7isect  bites  and  give  the  treatment. 


CHAPTER   XVIII 

THE   BLOOD 

272,  The  circulatory  system.  —  Nature  has  provided  an 
intricate  arrangement  of  tubes  to  conduct  food  to  each  cell 
of  the  body,  and  to  wash  away  its  waste  matter.  These 
two  objects  are  accomplished  by  the  blood.  The  conduct- 
ing tubes  and  the  blood  which  they  contain  make  the 
circulatory  system. 

273.  The  blood.  —  About  one  thirteenth  of  the  body  is  a 
red  liquid  called  blood.  It  consists  of  a  multitude  of  cir- 
cular flat  red  plates,  called  the  red  blood  coi'piLscles  or  cells, 
floating   in  a  colorless   liquid,  which  also  contains  a  few 

round    colorless   cells,  called    zvJiite   blood 


;"f  corpuscles  ^  cells. 
^  ©  ®*'®@         274.    Red    blood    corpuscles.  —  The    red 

c  8  t^   @®  corpuscles  of  the  blood  form  about  45  per 

Blood  corpuscles  Cent  of  its  weight.     Each  one  is  a  circular 

(X  400).  ^^^  plate,  with  rounded   edges,   and  with 

a  a  pile  of  red  blood  ,  •  •       .1  i.  r  u    r 

^g„5  a  depression   in  the  center   oi    each  lace. 

b  red   blood    cells.  Each    Cell    is   about  3-7-^00  ^^    ^^    vs\<z\v    in 

seen  flatwise.         ,.  ,  ,  ,  U  •       1      •        ^i  •    i 

c  red    blood    cells,  diameter   and   ysW^  ^^  ^^   ^^^^   ^^    thick- 
seen  edgewise,    ncss.      Each   ouc   is   of  a   reddish   yellow 

d  white  blood  cells.  .,     , 

color,  but  when  great  numbers  are  piled 
together  they  appear  bright  red.  Each  corpuscle  is  com- 
posed of  a  jellylike  albuminous  substance,  four  fifths  of 
which  is  a  reddish  substance  called   hemoglobm.      Hemo- 

156 


THE   BLOOD  1 57 

globin  is  the  essential  part  of  the  red  corpuscle.  It  con- 
tains a  small  amount  of  iron,  which  gives  to  it  the  prop- 
erty of  carrying  oxygen  without  itself  being  oxidized.  By 
means  of  the  hemoglobin  the  red  corpuscles  are  able  to 
carry  oxygen  from  the  lungs  to  all  parts  of  the  body. 
When  the  hemoglobin  contains  a  large  amount  of  oxy- 
gen the  blood  is  of  a  bright  red  color,  but  as  the  oxygen 
is  used  up  it  becomes  darker,  or  almost  purple.  Bright 
red  blood,  called  a7'terial  blood,  is  continually  flowing 
toward  the  cells  of  the  body ;  while  that  returning  from 
the  cells,  called  venous  blood,  is  purple  in  color,  from  the 
lack  of  oxygen. 

275.  White  corpuscles.  —  White  corpuscles  are  each 
about  -30^-00"  °^  ^^  vnQ^i  in  diameter,  and  are  about  -^-^  as 
numerous  as  the  red  corpuscles. 
They  are  round  and  colorless,  and 
each  contains  a  nucleus.  They 
have  the  power  of  changing  their 
shape,  and  of  adhering  to  the 
sides  of  a  blood  tube,  and  of 
passing  through  its  wall,  and  of 
moving  about  between  the  cells 

r   ,y       y      ^  ^i  ^  i  i        A  wMte  blood  cell  of  a  frog, 

of   the  body   as   though    endowed  sketched   at    intervals    of   two 

with   a  will   of   their   own.      They  or  three  minutes,  showing  its 

,  .  .      .  .  changes  in  form  (X300). 

have  important  duties  to  perform 

in  preventing  foreign  substances  from  entering  the  circula- 
tion and  in  the  healing  of  wounds.     (See  p.  393.) 

276.  Plasma.  —  The  Hquid  part  of  the  blood  is  called 
the  plasma.  It  is  composed  of  ninety  parts  of  water, 
holding  in  solution  about  eight  parts  of  albumin  and  two 
parts  of  mineral  matter.  The  mineral  matter  is  mostly  soda 
and  potash.  This  alkaline  property  of  the  blood  plasma 
aids  it  in  dissolving  carbonic  acid  gas,  and  in  carrying  it  to 


158 


APPLIED   PHYSIOLOGY 


the  lungs,  where  it  is  breathed  out  from  the  body. 
Some  of  the  mineral  matter  of  the  blood  enters  into  the 
composition  of  the  cells  of  the  body,  especially  of  bone 
cells. 

The  albumin  is  the  substance  out  of  which  all  of  the 
cells  of  the  body  are  mainly  built.  It  is  formed  by 
the  liver  out  of  the  peptone  which  was  absorbed  from  the 
intestine.  A  little  pressure  causes  the  solution  of  albumin 
and  minerals  to  how  through  the  sides  of  the  capillaries ; 
and  thus  it  reaches  the  separate  cells  of  the  body.  Waste 
matters  are  continually  being  poured  into  the  plasma,  but 
they  are  removed  as  fast  as  they  enter,  so  that  carbonic 
acid  is  the  only  one  to  be  found  except  by  the  most  deli- 
cate tests. 

277.  Clotting.  —  When  blood  is  drawn  from  the  body  it 
soon  becomes  a  jelly  like  mass,  called  a  clot.  After  a  longer 
time  the  clot  becomes  firmer  and  smaller,  squeezing  out  a 
clear,  straw-colored  liquid,  called  senwt.  The  process  of 
changing  blood  from  a  liquid  to  a  jellylike  form  is  coagu- 
lation, or  clotting.  In  the  process  a  part  of  the  albumin 
becomes  solidified  in  small  interlacing  strings,  called 
fibrin^  which  entangles  the  rest  of  the  blood  into  its 
meshes.  The  network  soon  contracts,  squeezing  out  the 
serum,  and  retaining  the  corpuscles.  The  serum  is  com- 
posed of  all  the  materials  of  the  plasma,  excepting  the 
fibrin.     The  process  may  be  represented  thus : 


Plasma  or 

+ 
Corpuscles 


albumin 

+ 

mineral  matter 

+ 

water 

•         •          •         •          •    ^ 

'  albumin 
+ 
Serum,  or  ■  mineral  matter 
+ 
+  I  water 

i  fibrin 
+ 
corpuscles 


THE  BLOOD  1 59 

While  the  blood  is  in  motion  within  a  healthy  blood 
tube,  no  clotting  occurs,  but  as  soon  as  blood  is  drawn, 
it  clots,  or  if  a  blood  vessel  is  wounded,  a  clot  forms  at 
the  wounded  spot.  The  use  of  clotting  is  to  stop  bleeding. 
Sometimics  no  clot  will  form,  but  a  wound  will  keep  on 
bleeding  until  it  is  healed.  This  is  a  disease  called  hemo- 
philia, and  may  cause  death. 

278.  Anemia.  —  Sometimes  there  are  too  few  red  cor- 
puscles in  the  blood.  Then  the  skin  appears  pale  and 
there  is  shortness  of  breath,  because  too  little  oxygen  is 
carried  by  the  diminished  number  of  red  blood  cells.  The 
disease  is  called  a^ieynia,  meaning  lack  of  blood.  It  is 
mainly  a  lack  of  red  corpuscles. 

279.  Good  and  bad  blood. — The  terms  good  and  bad  blood 
are  remnants  of  the  old  idea  that  disease  was  caused  by  watery  sub- 
stances, called  humors,  in.  the  blood.  From  their  supposed  influence 
on  the  mind  the  terms  good  and  bad  humored  are  derived. 

For  many  years  attempts  have  been  made  to  inject  healthy  blood 
into  the  veins  of  sick  persons.  Injecting  a  liquid  into  the  veins  of  a 
living  person  is  transfusion.  In  bleeding,  the  loss  of  water  is  one  of 
the  greatest  dangers,  and  to  replace  it  water  is  sometimes  injected  into 
the  veins.     It  answers  better  than  blood  itself. 

280.  The  blood  in  lower  animals.  —  All  living  beings 
possess  some  form  of  fluid  circulating  in  their  interior. 
In  higher  animals,  birds,  reptiles,  and  fishes,  the  fluid  is 
red,  and  contains  both  red  and  white  corpuscles.  In 
insects  the  blood  is  usually  white  or  colorless.  In  worms 
the  blood  is  sometimes  colorless  and  sometimes  red  or 
green.  In  shellfish  the  blood  is  colorless,  and  contains  no 
corpuscles.  In  animals  which  are  made  up  of  a  single 
microscopic  speck  of  matter,  there  seems  to  be  a  continual 
motion  of  fluid  within  their  bodies,  although  they  are  so 
extremely  small  that  nothing  definite  can  be  seen. 


l60  APPLIED   PHYSIOLOGY 

281.  The  spleen.  —  The  spleen  or  milt  is  a  soft  red 
organ,  shaped  Uke  a  tongue,  lying  just  to  the  left  of  the 
stomach.  It  is  composed  of  small  cells  and  fibers,  among 
which  the  blood  circulates  as  through  a  sponge,  without 
being  held  within  firm  walled  tubes.  The  spleen  is  sup- 
posed to  form  the  red  blood  cells,  but  they  are  also  formed 
in  the  marrow  of  bones.  The  spleen  can  be  removed  with 
but  little  harm  to  the  body.  The  pain  in  the  side  caused 
by  running  is  often  due  to  an  excess  of  blood  in  the  spleen. 

SUMMARY 

1.  Blood  is  composed  of  a  liquid  called  plasma,  in  which 

float  great  numbers  of  extremely  small  red  cells,  and 
fewer  white  cells. 

2.  The  red  cells  carry  oxygen  from  the  lungs  to  the  cells 

of  the  body. 

3.  The  white  cells  repair  injuries  to  the  body. 

4.  The   plasma    contains    albumin    and    mineral   matters^ 

both  of  which  are  food  for  the  cells  of  the  body. 

5.  The  soda  of  the  plasma  carries  carbonic  acid  gas  to  the 

lungs.     The  gas  is  there  given  off  in  the  breath. 

6.  After  standing  outside  of  the  body  for  a  few  minutes, 

some  of  the  albumin  hardens  to  a  stringy  mass  and 
entangles  the  cells,  forming  a  clot. 

7.  All  animals  possess  a  fluid  somewhat  like  man's  blood. 

8.  The  spleen  is  a  soft  organ  in  which  red  blood  cells  are 

formed. 

DEMONSTRATIONS 

64.  Set  aside  a  spoonful  of  chicketi's  blood  to  clot.  In  a  few  hours  the 
serum  will  begin  to  separate.  Breathe  on  a  slide  and  place  a  tiny  drop 
of  fresh  chicken's  blood  upon  it,  cover  it  with  a  cover  glass  and  exam- 
ine it  with  a  microscope  magnifying  at  least  200  diameters  to  see  the 
red  blood  cells.     Notice  their  oblong  shape  and  their  nuclei. 


THE   BLOOD  l6l 

65.  Human  blood  may  be  obtained  without  pain  by  tying  a  string 
snugly  around  the  finger.  After  a  moment  make  a  quick  prick  with 
a  clean  needle  upon  the  back  of  the  finger  just  behind  the  nail.  Remove 
the  string,  and  a  drop  of  blood  will  fiow  which  can  be  examined  under 
the  microscope.  Notice  the  circular  shape  of  the  red  cells  and  the 
absence  of  nuclei.  Notice  that  they  tend  to  arrange  themselves  in  rows 
like  piles  of  coins. 

66.  Place  a  drop  of  salt  water  on  the  slide  by  one  edge  of  the  cover 
glass,  and  notice  that  the  cells  become  shrunken. 

67.  White  blood  cells  are  too  few  in  number  to  be  readily  found 
within  a  specimen  of  blood,  but  they  form  most  of  the  white  matter  of 
a  pimple  or  boil.  Prepare  and  examine  a  specimen,  and  notice  the 
dark  specks  scattered  through  the  cells,  and  the  nuclei  which  may  be 
three  in  number  in  each  cell.  Add  a  drop  of  vinegar  and  notice  that 
each  cell  becomes  transparent,  only  the  nuclei  remaining  visible. 

68.  With  a  little  care  the  movement  of  the  white  cells  may  be  shown, 
in  frog's  blood.  Prepare  a  fresh  specimen  of  frog's  blood  upon  a  slide 
slightly  warmed.  After  a  little  search  an  irregularly  shaped  w^hite  blood 
cell  can  usually  be  found.  Watch  it  carefully,  and  it  will  be  seen  slowly 
changing  its  shape  exactly  as  an  ameba  changes,  only  more  slowly.  A 
magnifying  power  of  at  least  200  diameters  will  be  necessary. 

69.  Prepare  a  specimen  of  blood  for  the  microscope.  (See  demon- 
stration No.  65.)  At  the  edge  of  the  cover  glass  drop  a  tiny  bit  of 
alcohol.  Notice  how  the  red  blood  cells  shrivel  and  become  irregular 
in  form,  because  the  alcohol  takes  away  their  water. 

REVIEW  TOPICS 

1.  Describe  the  blood. 

2.  Describe  the  red  blood  cells. 

3.  Describe  the  white  blood  cells. 

4.  Describe  the  blood  plasma. 

5.  Describe  the  clotting  of  blood. 

6.  Show  what  was  meant  in  olden  times  by  the  terms  good 

and  bad  blood  and  good  and  bad  Jimnored. 

7.  Describe  the  blood  in  some  of  the  lower  forms  of  living 

beings. 

8.  Describe  the  spleen  and  its  use. 

OV.  PHYSIOL.  —  n 


CHAPTER   XIX 


THE   HEART 


/  — 

-  © 

t 

A* 

/ 

k 

jn. 

1 

282.    The  heart.  —  The  blood  is  kept  flowing  through  all 
parts  of  the  body  by  the  heart.     The  heart  is  essentially  a 

hollow  shell  of  muscles,  which 
has  the  power  of  squeezing  its 
sides  tightly  together,  so  as  to 
force  out  the  blood.  It  is  coni- 
cal in  shape.  Its  side  lies  upon 
the  diaphragm,  with  its  tip 
pointing  downward,  forward, 
and  to  the  left.  Its  small  end 
touches  the  chest  wall  about 
two  and  a  half  inches  to  the 
left  of  the  lower  end  of  the 
sternum  or  breastbone,  and  its 
large  end  extends  along  the 
right  side  of  the  breastbone, 
from  its  lower  end  upward  as 
high  as  the  third  rib.  It  is 
almost  covered  by  the  lung, 
and  is  inclosed  in  a  bag  of 
serous  membrane  called  the 
pericardium.  The  pericar- 
dium is  very  smooth,  so  as  to  permit  free  movements  of 
the  heart  within  it.      (See  cut,  p.  66.) 

162 


The  heart. 

right  ventricle. 

left  ventricle. 

artery  between  the  two  ventricles, 

nourishing  the  heart's  muscles, 
pulmonary  artery, 
left  auricle, 
aorta. 

artery  to  left  side  of  head, 
artery  to  left  arm. 
artery  to  right  side  of  head, 
artery  to  right  arm. 
descending  vena  cava, 
right  auricle. 


VI   ascending  vena  cava. 


THE    HEART 


163 


283.  Cavities  of  the  heart.  —  The  heart  is  designed  to 
pump  two  separate  streams  of  blood  at  once.  Its  left  side 
pumps  blood  through  the 
whole  body,  while  its  right 
side  pumps  it  only  through 
the  lungs.  The  cavity  on 
each  side  is  partly  divided 
into  an  upper  chamber  called 
an  auricle,  and  a  lower  one 
called  a  ventricle.  Each 
auricle  has  thin,  flabby  walls, 
and  does  little  of  the  work  of 
pumping  blood. 

The  ventricles  have  thick 
and  strong  walls,  which  form 
nearly  all  the  bulk  of  the 
heart.  The  left  ventricle  has 
walls  three  times  as  thick  as 

the  right  ventricle,  for  it  must    a   artery  with  its  lower  end  split  open 
^  ^        ^    .^  ^  ^      b    vein  leading  into  the  heart. 

pump  blood  through  a  much 
greater  part  of  the  body. 
From  each  ventricle  a  tube, 
called  an  artery,  conducts  the 
blood  away. 

284.  Valves  of  the  heart. 
—  Blood  enters  each  auricle 
through  tubes  called  vei7is, 
and  streams  through  the 
opening  into  the  ventricle,  ^ 
but  is  prevented  from  flow- 
ing back  by  thin,  strong  cur- 
tains which  are  attached  to  the  edge  of  the  opening  and 
hang  suspended  in  the  ventricle. 


Valves  of  the  heart. 


c    auricle  with  the  front  cut  away. 

d  cut  edge  of  the  auricle,  showing  its 

thinness. 
e    semilunar  valves ;    their  upper  edges 

are  free  and  movable. 
f  mitral  valve  spread  open. 
g  strings  from  the  edge  of  the  curtain 

of  the  valve  to  steady  it. 
k   muscular  projection  upon  the  inside 

of  the  ventricle  to  which  the  strings 

are  attached. 
i    indentations  upon  the  inner  surface  of 

the  ventricle, 
wall  of  the  ventricle,  showing  its  thick- 
ness as  compared  with  that  of  the 

auricle,  d. 


From  the  edges  of  each 


164 


APPLIED   PHYSIOLOGY 


curtain  fine  threads  extend  to  projections  upon  the  muscu- 
lar walls  of  the  ventricle,  to  keep  the  curtains  smooth  and 
straight.  Blood  flowing  from  the  auricle  into  the  ventricle 
readily  separates  the  curtains,  but  blood  pressing  upon 
them  from  the  ventricle  forces  them  tightly  together,  so 

that  not  a  drop  can  pass 
through.  Thus  they  form 
a  valve  in  each  opening. 
The  valve  upon  the  left 
side  is  composed  of  two 
curtains,  and  is  called  the 
mitral  valve.  The  one 
on  the  right  side  is  com- 
posed of  three  curtains 
and  is  called  the  tricuspid 
valve.  From  their  situa- 
tion, these  valves  are 
often  called  the  aiiricido- 
ve7itricular  valves. 

285.    Semilunar   valve. 


Systole  of  the  heart. 

vein  entering  the  auricle, 
auricle. 


closed  valve  to  keep  blood  from  flowing    —  At    the     beginning    of 
back  into  the  auricle. 
d  ventricle. 
e    artery. 


each  artery  leading  from 
the  ventricles   are    three 

^  'tentdct!'^  ^^"""^  ^'""^  ''^'''"'"^  *°  '^'  thin,  silklike  flaps,  shaped 

like  half-moons.  They 
are  arranged  so  that  blood  flowing  from  the  ventricle  pushes 
each  flap  against  the  side  of  the  artery ;  but  between  the 
beats  of  the  heart,  the  blood  in  the  artery  presses  backward, 
forcing  the  flaps  away  from  the  side  of  the  artery,  so  that 
they  all  meet  tightly  in  the  middle.  They  form  a  valve 
called  the  semilunar  valve,  from  the  shape  of  each  flap. 

286.    Action  of  the  heart.  —  The  heart  is  a  pump  with 
valves  permitting  blood  to  flow  through  an  auricle  into  a 


THE   HEART 


165 


ventricle  and  out  into  an  artery,  while  preventing  any  flow- 
in  the  opposite  direction. 

As  blood  enters  the  heart  it  passes  through  the  auricles 
into  the  ventricles.  Just  before  the  ventricles  are  full  the 
auricles  suddenly  contract  and  drive  the  blood  into  the 
ventricles,  which  are 
thus  filled  full  and  im- 
mediately begin  to  con- 
tract, while  the  auricles 
relax.  The  pressure 
closes  the  mitral  and 
tricuspid  valves  and 
opens  the  semilunar 
valves.  The  blood  is 
thus  prevented  from 
flowing  back  to  the  auri- 
cles, but  flows  through 
the  open  entrance  to  the 
arteries.  During  the 
contraction  of  the  ven- 
tricles, the  auricles  re- 
main relaxed  and  receive 
the  blood  returning  to 
the  heart. 

When  all  the  blood  is 
expelled  from  the  ventricle  it  relaxes,  and  the  blood  falls 
back  upon  the  semilunar  valves,  closing  them  so  that  none 
returns.  At  the  same  time  the  blood  in  the  auricles  presses 
open  the  mitral  and  tricuspid  valves,  and  again  fills  the 
ventricles. 

287.  Rate  and  time  of  the  hearths  action.  — The  contrac- 
tion of  the  heart  is  called  its  systole,  and  its  relaxation  its 
diastole.     At   each    systole   from   two    to   four  ounces  of 


Diastole  of  the  heart. 

a  blood  entering  auricle. 

b  auricle. 

c  open  valve  to  permit  blood  to  flow  into  the 

ventricle. 

d  ventricle. 

e  artery. 

f  closed  semilunar  valve. 


1 66  APPLIED   PHYSIOLOGY 

blood  are  expelled.  It  occurs  about  seventy-two  times 
each  minute.  While  the  heart  beats  occur  regularly 
without  apparent  pause,  yet  it  rests  in  diastole  about 
one  half  the  time. 

288.  Sounds  of  the  heart.  —  Two  sounds  are  produced  by  each 
beat,  which  may  be  heard  by  hstening  with  the  ear  close  to  the  heart. 
The  first  sound  is  the  longer  and  softer,  and  is  caused  by  the  vibration 
of  the  contracting  muscles.  The  second  sound  is  shorter  and  sharper, 
and  is  caused  by  the  sudden  closing  of  the  semilunar  valves.  At  each 
systole  the  portion  of  the  heart  touching  the  wall  of  the  chest  may  be 
felt  to  become  suddenly  harder,  as  though  it  beat  against  the  chest 
wall.  Its  movements  are  transmitted  through  the  chest  walls  so  that 
they  may  be  plainly  seen  and  felt.  Ordinarily  a  person  is  not  aware  of 
his  own  heart  beats,  but  when  they  are  very  forcible  they  are  plainly 
felt,  and  are  called  palpitation. 

289.  Nerves  of  the  heart.  —  A  nervous  mechanism  within 
the  heart  itself  causes  it  to  contract  even  after  it  is  sepa- 
rated from  the  body.  A  fish's  or  turtle's  heart  will  con- 
tract regularly  for  hours  after  being  removed  from  the 
body.  Man's  heart  is  easily  affected  by  outside  influ- 
ences, but,  because  of  its  own  nervous  mechanism,  it  is 
not  so  sensitive  as  has  been  supposed.  Wounds  com- 
pletely penetrating  the  ventricle  have  been  sewed  up,  and 
recovery  has  taken  place.  The  action  of  the  heart  is  regu- 
lated and  adapted  to  the  varying  needs  of  the  body  through 
two  sets  of  nerves,  one  set  from  the  brain  and  the  other 
set  from  the  spinal  cord.  In  physical  exertion  the  spinal 
nerves  cause  it  to  beat  faster  and  more  forcibly.  This 
adaptation  is  so  delicate  that  rising  from  a  sitting  to  a  stand- 
ing position  perceptibly  increases  the  number  of  heart  beats. 
Joy,  or  anger,  or  excitement  of  any  kind  hastens  its  action, 
while  grief  usually  retards  and  weakens  it. 

290.    Effect  of  violent  exercise.  —  In  prolonged  and  vio- 
lent physical  exercise  the  heart  performs  more  work  than 


THE   HEART  167 

is  natural,  and  grows  larger  to  accommodate  itself  to  the 
strain.  Repeated  calls  to  extra  exertion  may  cause  it  to 
respond  more  quickly  and  with  more  vigor  than  occasion 
demands,  so  that  a  slight  excitement  or  exertion  causes 
palpitation.  Those  who  engage  in  races  are  especially 
liable  to  overwork  their  hearts. 

291.  Palpitation  of  the  heart.  —  The  response  of  the  heart 
to  influences  from  the  outside  may  be  excessive,  so  that  it  beats  too 
quickly  and  more  forcibly  than  occasion  demands.  Sudden  noises, 
and  excitement  of  any  kind,  cause  the  heart  to  beat  violently  or  palpi- 
tate in  some  persons.  But  palpitation  of  the  heart  is  an  annoyance 
rather  than  a  disease.  While  the  will  has  no  control  over  the  heart, 
yet  it  can  control  the  emotions  which  cause  the  palpitations.  Persons 
of  calm  temperament,  who  exercise  self-control  over  their  emotions,  are 
rarely  troubled  with  palpitation.  Our  words  ending  in  ''hearted,"  as 
"  warm.-hearted,"  are  records  of  the  old  belief  that  the  heart  governed 
the  feelings  instead  of  the  feelings  aiTecting  the  heart. 

292.  Fatty  heart. — The  heart  may  become  diseased, 
but  heart  disease  is  by  no  means  so  dangerous  as  is  com- 
monly supposed.  In  fact,  those  having  diseased  hearts 
are  usually  unaware  of  it  for  years,  while,  on  the  other 
hand,  those  who  think  their  hearts  are  diseased  are  almost 
always  mistaken. 

There  is  a  common  change  of  the  heart's  muscle,  in  which  little 
particles  of  the  muscle  cells  are  changed  to  fat.  The  cells  are  thus  weak- 
ened, and  made  unable  to  respond  to  a  sudden  extra  demand.  A  per- 
son with  excessive  development  of  fat  elsewhere,  is  liable  to  have  a 
fatty  heart.  Avoidance  of  things  w^hich  tend  to  cause  excitement  and 
overwork  will  enable  such  a  heart  to  work  on  without  noticeable  change 
in  its  actions. 

293.  Disease  of  the  valves  of  the  heart.  —  The  other 
common  form  of  heart  trouble  is  a  thickening  and  puck- 
ering of  the  valves,  causing  a  leakage  so  that  some  blood 
flows  backward.     But  the  heart  grows  larger  and  stronger, 


l68  APPLIED   PHYSIOLOGY 

SO  that  it  can  pump  enough  blood  to  supply  the  body  in 
spite  of  the  constant  leakage  backward.  The  heart  may 
thus  become  twice  its  natural  size,  but  there  is  a  limit  to 
its  enlargement,  and  finally  it  grows  weak.  If  exertion 
is  avoided,  such  a  heart  may  work  perfectly  for  years. 

The  nervous  system  contained  in  the  heart's  muscle  makes  it  the 
most  resistant  of  all  the  organs  of  the  body,  and  the  one  whose  disease 
is  least  to  be  feared.  It  is  the  first  organ  formed  in  the  child,  and  is 
the  last  to  die.  When  it  begins  to  fail,  the  blood  accumulates  in  the 
lowest  parts  of  the  body,  and  produces  swelling  of  the  feet,  which  is 
one  of  the  first  signs  of  heart  disease. 

294.  Fainting.  —  When  the  heart  is  suddenly  checked 
and  made  weak  in  its  action  to  such  an  extent  that  little 
blood  is  driven  to  the  brain,  unconsciousness  and  complete 
loss  of  muscular  power  result,  so  that  the  person  falls  to 
the  ground.  The  face  appears  pale,  because  there  is  but 
little  blood  in  it.  This  paleness  and  loss  of  consciousness 
is  0.2^0,^  fainting.  When  a  person  faints  he  should  be  laid 
upon  his  back  with  his  head  as  low  as  his  body,  so  that  the 
blood  may  flow  to  the  brain  more  easily.  Cold  water  should 
be  thrown  upon  the  face  so  that  the  sudden  shock  may 
stimulate  the  spinal  nerves  which  hasten  the  heart's  action. 
In  a  few  seconds  the  heart  beats  become  stronger,  and  con- 
sciousness is  regained.  Remember  7iot  to  raise  the  head 
of  a  fainting  person. 

295.  Effects  of  alcohol  upon  the  heart.  —  The  first  effect 
of  alcohol  is  to  increase  the  force  and  frequency  of  the 
heart  beats.  This  sends  more  blood  through  all  the  body, 
and  there  is  a  feeling  of  greater  strength,  which  is  called 
stimulation.  Men  take  strong  drink  for  this  effect.  This 
feeling  comes  on  within  a  few  minutes  after  drinking 
and    passes   off    in   the    course    of   an    hour.      Then   the 


THE   HEART  169 

drinker  feels  a  desire  for  more  alcohol  and  so  forms  a 
habit  of  its  use.  While  a  little  alcohol  may  make  a  man 
feel  better,  yet  the  strength  and  endurance  of  his  heart 
is  really  diminished.  Alcohol  is  like  a  whip  which  makes 
the  heart  beat  harder  for  a  time  but  leaves  it  less  able 
to  do  its  work  in  the  future.  Its  blow  is  pleasant  at  the 
time  it  is  given,  but  it  is  all  the  more  harmful  because 
it  is  enjoyed. 

296.  Effects  of  continuous  drinking.  —  The  derangement 
of  digestion  and  assimilation  resulting  from  long-continued 
drinking  impairs  the  nutrition  of  the  whole  body,  includ- 
ing the  heart.  Drinkers  confound  the  absence  of  fatigue 
with  strength  itself. 

297.  Effects  of  tobacco  upon  the  heart.  —  Tobacco  used 
in  any  form  is  a  direct  poison  to  the  heart's  muscle  and 
causes  it  to  beat  with  less  strength.  When  a  large  amount 
is  used,  it  poisons  the  nerves  of  the  heart  and  hinders  their 
harmonious  action.  Then  the  heart  will  beat  irregularly, 
and  there  will  be  palpitation  on  slight  exertion,  so  that 
hard  physical  exercise  becomes  an  impossibility.  The 
trouble  may  be  only  an  inconvenience,  so  that  the  person 
cannot  engage  in  violent  exercise ;  but  in  its  severe  forms 
it  may  be  the  cause  of  death. 

SUMMARY 

1.  The   blood    is   kept   in   constant   motion  by  a  double 

muscular  pump,  called  the  heart. 

2.  The   heart  contains   two   pairs   of   cavities,  each  con- 

sisting of  an  auricle  and  ventricle. 

3.  Between  each  auricle   and  ventricle  there  is   a  valve 

which  permits  blood  to  flow  into  the  ventricle,  but 
keeps  it  from  flowing  back. 


I/O  APPLIED    PHYSIOLOGY 

4.  Each  ventricle  contracts  upon  the  blood  about  seventy- 

two  times  a  minute,  forcing  it  out  through  a  tube 
called  an  arte?y. 

5.  Blood  is  kept  from  running  back  into  the  heart  by  a 

valve  at  the  beginning  of  the  artery. 

6.  The    heart    contains    a    nervous    mechanism    which 

makes  it  partially  independent  of  the  rest  of  the 
body. 

7.  The    heart  has    great    power    of    resistance    against 

disease,  and  of  accommodating  itself  to  increased 
work,  so  that  heart  disease  is  less  to  be  feared 
than  disease  of  almost  any  other  part  of  the 
body. 

8.  Alcohol  at  first  causes  the  heart  to  beat  faster  and 

more  strongly  than  the  body  needs,  thus  causing 
it  to  tire  itself  out. 

9.  Alcohol  soon  weakens  the  heart  by  impairing  its  nutri- 

tion. 
10.    Tobacco  makes  the  heart  beat  irregularly  and  with 
less  power. 

DEMONSTJ^ATIONS 

yo.  The  left  side  of  a  chicken's  heart  closely  resembles  a  man's 
left  auricle  and  ventricle,  and  can  be  used  to  show  the  cavities  and 
valves.  In  removing  it,  be  careful  to  preserve  its  covering  of  peri- 
cardium. A  pig\s,  or  sheep's,  or  bullock's  heart  is  more  like  a  human 
heart.  The  butcher  should  be  instructed  not  to  cut  off  the  auricles. 
(See  demonstration  35.) 

71.  The  heart  of  a  frog  or  fish  which  has  just  been  killed  should  be 
removed  to  show  its  persistence  in  beating.     (See  demonstration  35.) 

72.  Have  the  students  listen  to  each  other's  hearts  so  as  to  get 
a  clear  idea  of  the  two  sounds.  Feel  the  heart  beats  upon  the  chest, 
and  notice  how  they  increase  in  force  and  frequency  when  a  person 
rises  after  lying  down,  and  more  yet  when  he  walks  and  runs. 


THE    HEART  I /I 

REVIEW  TOPICS 

1.  Describe  the  heart:    its  situation,  pericardium,  cavi- 

ties, and  valves. 

2.  Describe  the  action  of  the  heart  and  the  flow  of  blood 

through  it. 

3.  Describe  what  may  be  heard,  seen,  and  felt  by  examin- 

ing the  body  over  the  heart. 

4.  Describe  the  nervous  mechanism  of  the  heart. 

5.  Give  the  effect  of  violent  exercise  upon  the  heart. 

6.  Discuss  palpitation  of  the  heart. 

7.  Describe  a  fatty  heart. 

8.  Describe  how  the  valves  of  the  heart  may  be  diseased. 

9.  Describe  fainting  and  its  treatment. 

10.  Give  the  effects  of  alcohol  upon  the  heart. 

11.  Give  the  effects  of  tobacco  upon  the  heart. 


CHAPTER   XX 


THE  FLOW   OF  BLOOD   IN  THE   BODY 


298.    Arteries.  —  The   tubes   which   conduct    the    blood 
away  from  the  heart  are  called  arteries.     From   the   left 

ventricle  there  goes  a  single 
tube  called  the  aorta.  It 
gives  off  branches,  which 
subdivide  again  and  again, 
a  until  they  are  of  micro- 
scopic size  and  penetrate 
to  every  part  of  the  body. 
From  the  right  ventricle 
there  extends  another  tube, 
called  \}ci^  pithnoiiary  artery^ 
which  conducts  blood  only 
to  the  lungs,  where  it  is 
purified. 

299.  Structure  and  action 
of  arteries.  —  An  artery  is  a 
muscular  tube  covered  with 
a  tough  layer  of  connective  tissue  and  lined  with  a  layer 
of  very  smooth,  platelike  cells.  Its  muscle  can  diminish 
the  size  of  the  tube.  The  arteries  are  elastic,  and  are 
always  so  full  of  blood  that  they  are  somewhat  distended. 
At  each  systole  of  the  heart,  from  two  to  four  ounces  of 
additional  blood  are  suddenly  forced  into  the  already  full 
aorta.     During  the  heart's  diastole,  the  elasticity  of  the 

172 


An  artery  cut  across  (X  200). 

a  smooth  inner  coat. 

b  middle  or  muscular  coat. 

c  outer  or  connective  tissue  coat. 

d  small  artery  to  nourish  the  large  one. 


THE   FLOW  OF   BLOOD   IN  THE   BODY 


173 


artery  causes  it  to  contract,  forcing  the  blood  onward  in 
a  steady  stream.  But  the  artery  can  exert  no  more  power 
in  contracting  upon  its  blood  than  the  heart  exerted  in 
distending  the  artery,  and  so  it  is  really  the  heart's  force 
which  propels  the  blood. 

300.  The  pulse.  —  The  extra  distention  of  the  aorta  by 
each  systole  of  the  heart  produces  a  wave  in  the  blood 
which  runs  along  the  arterial  tubes.  Wherever  an  artery 
runs  near  the  surface,  as  in  the  wrist,  the  wave  may  be 
felt,  and  is  called  the  pulse.  The  pulse  is  not  a  sudden 
current  of  blood  shot  through  the  artery,  but  is  a  wave 
in  the  steady  stream.  By  means  of  the  pulse  the  fre- 
quency and  regularity  of  the  heart  beats  may 
be  determined.  When  an  artery  is  cut,  a 
continuous  jet  of  blood  spurts  out  to  a  con- 
siderable distance,  which  momentarily  in- 
creases in  size  with  each  wave  beat. 

301.  Capillaries.  —  The  smallest  arteries 
suddenly  divide  into  an  extremely  fine  net- 
work of  tubes,  called  capillaries.  Each  capil- 
lary tube  is  from  2  oVo  ^^  30^00  of  an  inch  in 
diameter,  and  from  yoVo"  ^^  5V  ^^  ^^  ^^^'^  ^^ 
length.  It  is  composed  of  the  same  kind  of 
smooth  and  flat  cells  as  those  which  line  the 
arteries ;  in  fact,  the  capillaries  are  the  pro-      Diagram  of  a 

lono^ation  of  the  lininsfs  of  the  arteries.    They  capillary,  show- 

1  ,  ,  11        r     1        ing  the  platelike 

penetrate  the  spaces  between  the  cells  of  the  cells  of  which  it 

body  in  such  a  close   network  that   several  ^^  composed  (x 

.  1      .  .  500)- 

capillaries  may  be  m  contact  with  each  cell, 

and  the  point  of  a  fine  needle  cannot  be  thrust  into  the 

body  without  wounding  some.    The  blood  in  the  capillaries 

gives  the  pink  tinge  to  the  skin,  which  disappears  when 

the  blood  is  pressed  out.      The  total  capacity  of  the  capil- 


174 


APPLIED   PHYSIOLOGY 


laries  is  about  three  hundred  times  that  of  the  arteries, 
and  hence  the  blood  pressure  is  much  less  than  in  them ; 

yet  the  pressure  is  always 
sufficient  to  keep  the  blood 
in  steady  motion. 


^e^ 


302.  Action  of  the  white 
blood  cells  in  the  capil- 
laries. —  Often  a  white  blood 
cell  will  adhere  to  the  wall  of 
the  capillary  and  partially  block 
the  blood  stream  for  a  moment. 
It  may  work  its  way  through 
the  wall  of  a  capillary,  and  yet 
leave  no  hole  behind  it.  Many 
are  thus  found  in  the  spaces 
outside  the  capillaries,  and  are 
finally  returned  to  the  heart  by 
means  of  another  set  of  tubes 
called  lyi)iphatics.  When  a  capillary  is  injured,  many  of  the  white 
cells  adhere  to  the  injured  spot  and  furnish  food  for  its  repair.  They 
may   even    grow    and   change 


"V/^^ 


Arrangement  of  capillaries. 

a  smallest  artery. 

b   smallest  vein. 

c    network  of  capillaries. 


to    connective 
further  repair. 


tissue    for    its 


303.  Diffusion  of  blood 
plasma  in  the  capillaries. 
—  The  slight  pressure  to 
which  the  plasma  is  sub- 
jected is  just  sufficient  to 
cause  it  with  its  albumin 
to  diffuse  through  the  ex- 
ceedingly thin  wall  of  the 
capillary.       It     fills     the 

spaces  between  the  capillary  network  and  bathes  each  cell 
of  the  body  with  an  abundant  supply  of  nourishment. 


Diagram  showing  how  food  reaches  the 
cells  from  the  capillaries. 


THE   FLOW    OF   BLOOD    IN   THE   BODY  1 75 

304.  Exchange  of  oxygen  and  carbonic  acid  in  the  capil- 
laries. —  The  blood  in  a  capillary  is  separated  from  a  living 
cell  of  the  body  by  a  wall  so  thin  that  it  is  no  hindrance 
to  the  passage  of  oxygen  from  the  red  blood  cells.  In 
return  for  the  oxygen  received  from  the  blood,  the  body 
cells  give  out  carbonic  acid  gas,  which  passes  through  the 
capillary  walls  into  the  blood  as  readily  as  the  oxygen 
passes  in  the  opposite  direction.  A  given  particle  of 
blood  remains  in  a  capillary  only  a  second  at  most,  and 
in  that  time  there  occurs  an  exchange  of  oxygen  and 
nutritive  matter  between  the  blood  and  the  body  cells. 
Arteries  are  simply  tubes  which  conduct  blood  to  the 
capillaries,  where  all  the  actual  work  of  nourishing  the 
cells  is  performed. 

305.  Veins.  —  The  network  of  capillaries  at  the  end  of 
each  artery  unites  to  form  a  single  tube,  called  a  vein. 
Each  vein  unites  with  others  again  and  again,  to  form 
larger  tubes  which  run  alongside  of  each  artery,  and  finally 
all  unite  to  form  two  main  veins.  One  vein,  called  the 
descendiiig  vena  cava,  returns  blood  from  the  head  and 
arms ;  the  other,  called  the  ascending  ve^ia  cava,  returns 
blood  from  the  lower  extremities  and  trunk.  Each  opens 
into  the  right  auricle.  The  veins  have  about  three  times 
the  capacity  of  the  arteries.  Their  walls  are  composed  of 
the  same  material,  but  are  very  much  thinner,  for  they  do 
not  have  to  stand  much  pressure  of  blood.  The  blood 
current  is  correspondingly  slow.  The  veins  have  valves 
at  intervals  which  permit  of  a  free  flow  toward  the  heart, 
but  oppose  its  passage  backward,  so  that  when  a  vein  is 
pressed  the  blood  is  forced  only  towards  the  heart.  The 
contraction  of  the  muscles  pressing  upon  the  veins  is 
thus  a  great  aid  to  the  flow  of  blood.  The  flow  of  blood 
is  also  aided  by  the  movements  of  the  chest  in  breathing, 


176 


APPLIED   PHYSIOLOGY 


^J^~:^^% 


which  suck  venous  blood  toward  the  heart  just  as  it  sucks 

air  into  the  lungs. 

306.    Pulmonary  circulation.  —  As  the  blood  enters  the 

veins  from   the  capillaries,  it  has  lost  some  oxygen  and 

gained  carbonic 
acid  gas  and  other 
waste  matter.  This 
makes  it  much 
darker  in  color. 
Before  it  is  used 
again  it  is  purified 
and  given  a  new 
supply  of  oxygen. 
For  this  purpose 
it  is  sent  to  the 
lungs  as  soon  as  it 
reaches  the  heart. 
From  the  veins 
the  blood  flows  in- 
to the  right  side 
of  the  heart,  and 
then  to  the  lungs 
through  the  pul- 
monary artery. 
The  pulmonary 
artery  divides 
again  and  again 
into  small  twigs, 
and    these    divide 

into    a    close    net- 
Diagram  of  the  course  of  the  blood  in  the  circulation.     v;y^p,|.i,  ^f  canillaries 

within  the  lungs,  where  the  blood  is  separated  from  the  air 
by  only  the  thin  walls  of  the  capillaries.     Through  these 


THE  FLOW  OF  BLOOD   IN  THE   BODY  177 

thin  walls  the  oxygen  of  the  air  readily  penetrates  to  the 
red  blood  cells;  and  the  carbonic  acid  gas  just  as  readily 
passes  from  the  blood  to  the  air.  As  a  result  of  this 
change,  the  blood  becomes  of  a  bright  red  color,  and  is 
called  arterial  blood.  From  the  capillaries  of  the  lung  the 
arterial  blood  is  collected  into  the  pulmonary  veins  and 
carried  to  the  left  auricle,  and  then  to  the  left  ventricle, 
where  it  is  ready  to  make  another  circuit  of  the  body. 

307.  Summary  of  the  circulation  of  the  blood.  —  In  making 
a  complete  circuit  of  tlie  body  the  blood  passes  through  the  left  auricle, 
and  through  the  mitral  valve  to  the  left  ventricle ;  then  past  the  left 
semilunar  valve  to  the  aorta,  and  then  through  the  arteries  to  all  parts 
of  the  body ;  then  through  the  capillaries  into  the  veins,  and  back  to 
the  heart ;  next  through  the  right  auricle,  then  the  right  ventricle, 
then  through  ^^^  pulmonary  artery  to  the  capillaries  of  the  lung-,  then 
through  the  pulmonary  veins  to  the  left  auricle  once  more.  Thus  in 
making  the  complete  circuit  of  the  body,  a  drop  of  blood  passes  through 
the  heart  twice,  and  through  two  different  sets  of  capillaries.  The 
circuit  of  the  body  in  general  is  called  the  systemic  circulation,  and  that 
through  the  lungs  is  tho.  pulmonary  circulation. 

308.  The  portal  system  of  circulation.  —  The  blood  from 
the  capillaries  of  the  stomach  and  intestine  is  collected 
into  a  single  vein,  called  the  portal  vein,  which  goes  to  the 
liver  and  there  divides  into  capillaries.  The  liver  capil- 
laries can  be  considered  as  millions  of  small  tubes  which 
are  substituted  for  a  few  inches  of  the  portal  vein.  Just 
outside  of  the  liver  they  empty  into  three  veins  which 
open  into  the  ascending  vena  cava.  The  circulation 
through  the  liver  is  sometimes  called  the  poj'tal  circulation. 

309.  Time  required  in  the  complete  circulation. — It  re- 
quires about  twenty  seconds  for  a  drop  of  blood  to  go  the  round  of  the 
circulation  from  the  left  ventricle  back  to  its  starting  point.  All  the 
blood  passes  through  the  heart  about  once  every  two  or  three  minutes. 
All  the  arteries,  except  the  pulmonary  artery,  carry  bright  red  arterial 

ov.  PHYSIOL. —  12 


1/8 


APPLIED    PHYSIOLOGY 


blood,  while  all  the  veins,  excepting  the  pulmonary  veins,  carry  dark 
red  or  venous  blood. 

310.  The  lymph.  —  In  order  to  nourish  the  body,  the 
plasma  of  the  blood  is  continually  being  diffused  through 
the  capillaries  into  the  spaces  between  the  living  cells. 
Each  cell  is  thus  bathed  in  a  plentiful  supply  of  plasma, 
from  which  it  absorbs  its  nutriment.  The  spaces  also 
contain  many  white  cells,  which  have  left  the  capillaries. 
The  blood  plasma  and  blood  cells  filling  the  spaces  be- 
tween the  cells  are  called  the  lymph,  and  the  spaces  are 
called  lymph  spaces. 

The  lymph  is  a  thin,  colorless  fluid.  In  fact,  it  is  blood 
without  the  red  corpuscles,  but  with  many  waste  matters 
from  the  cells  of  the  body  added.  The  lacteals  of  the 
_  intestine   are  also 

'\rw^^^t3iy"V  lymphatics  which 

carry  the  digested 
fats,  and  hence 
their  lymph  is  of  a 
milky-white  color. 
311.  Lymphatics. 
—  Lymph  is  con- 
tinually collecting, 
and  its  removal  is 
provided  for  by 
means  of  a  set  of 
tubes,  called  the 
lymphatics.  The 
smallest  lymphatic 
tubes  are  much 
smaller  than  a  capillary,  and  their  walls  are  so  thin  that 
they  can  scarcely  be  seen  with  a  microscope.  Each  begins 
in  the  open  space  between  a  capillary  and   a  cell  of  the 


Lymphatics  of  the  head  and  neck. 
B  thoracic  duct. 


THE  FLOW   OF  BLOOD   IN  THE  BODY 


179 


body.  They  unite  again  and  again  to  form  about  twenty 
main  trunks  for  each  Umb.  Each  trunk  extends  upward, 
and  most  of  them  finally  unite  to  form  a  tube  of  the  size 
of  a  goose  quill,  called  the  thoracic  duct. 

The  thoracic  duct  lies  upon  the  spinal  column,  and 
extends  upward  into  the  neck,  where  it  opens  into  a  large 
vein.  The  lymphatics  have  numerous  valves,  all  opening 
toward  the  heart.  They  prevent  the  backward  flow  of  lymph. 

312.  Lymph  nodes.  —  At  irregular  intervals  the  lym- 
phatics open  into  small,  baglike  bodies  composed  of  a 
spongy  network  of  fibers  filled  with 
cells  which  look  like  white  blood 
cells.  Each  body  is  called  a  lymph 
glajtd  or  node.  The  lymph  flows 
through  these  nodes  as  water  flows 
through  a  filter.  They  strain  out 
matters  which  are  injurious  to  the 
system,  while  their  cells  envelop 
and  destroy  poisons.  Some  of  the 
cells  also  flow  on  with  the  lymph 
and  become  white  blood  cells. 

The  lymph  nodes  may  be  felt  in 
the  neck  and  groins  and  armpits,  as 
small  kernels  about  the  size  of  a 
grain  of  wheat  or  corn.  When  the 
lymph  carries  certain  kinds  of  poi- 
sons, they  swell  up  and  produce  the 
disease  called  scrofula.  In  boils, 
erysipelas,     and     other     inflamma-     t       -u     =      ^         1 

-^     ^         '  Lymph  node  and  vessels 

tions,  they  swell  and   become  very  (xio). 

tender  and  sometimes  break  down  and  form  abscesses. 

313.  Flow  of  the  lymph.  —  A  little  pressure  transmitted 
from  the  blood  in  the  capillaries  is  exerted  upon  the  lymph, 


l8o  APPLIED   PHYSIOLOGY 

but  not  enough  to  force  it  along  the  lymphatics.  Its  flow 
is  aided  by  the  pressure  of  muscles  upon  the  spaces  and 
the  tubes.  Its  current  is  slow  and  unsteady.  It  is  finally 
poured  through  the  thoracic  duct  into  a  vein  at  the  root  of 
the  neck,  where  it  mingles  with  the  blood.  About  two 
quarts  of  lymph  pass  through  the  thoracic  duct  daily.  If 
a  hollow  needle  is  thrust  into  the  skin,  and  through  it 
water  containing  medicine  is  forced,  the  medicated  water 
spreads  through  the  lymph  spaces  between  the  living 
cells.  Some  is  taken  up  by  the  capillaries,  and  some  passes 
into  the  circulation  by  means  of  the  lymph,  and  produces 
the  same  effect  as  though  it  entered  the  blood  through  the 
stomach. 

Sometimes  the  lymph  cannot  be  removed  by  the  lym- 
phatics so  fast  as  it  is  poured  out  by  the  capillaries.  It 
then  distends  the  lymph  spaces,  producing  uniform 
swellings  called  dropsy.  Dropsy  can  be  recognized  by  a 
small  pit  remaining  when  the  finger  is  pressed  into  the 
skin. 

314.  The  circulation  in  lower  animals.  —  Land  animals 
and  birds  possess  a  heart  and  blood  tubes  like  man's,  and 
their  circulation  follows  the  same  order.  The  heart  of  rep- 
tiles and  toads  consists  of  two  auricles  and  one  ventricle, 
and  the  ventricle  always  contains  both  arterial  and  venous 
blood. 

Fishes  possess  only  one  auricle  and  one  ventricle.  The 
ventricle  forces  the  blood  through  two  sets  of  capillaries, 
and  the  circulation  is  made  correspondingly  sluggish. 

Insects  possess  a  row  of  eight  or  nine  sacks  connected 
by  a  tube,  with  valves  opening  toward  the  head.  The 
contraction  of  the  sacks  forces  the  blood  toward  the  head, 
where  it  escapes  into  the  lymph  spaces  between  the  cells. 
There  are  no  arteries  or  veins,  and  so  the  blood  is  slowly 


THE  FLOW  OF  BLOOD  IN  THE  BODY        l8l 

forced  toward  the  back  part  of  the  body  through  the 
lymph  spaces  until  it  again  reaches  the  tube.  Their  cir- 
culation is  thus  like  the  circulation  of  lymph  in  man. 

Shellfish  usually  possess  a  heart  and  arteries  and  veins. 
In  the  very  lowest  animals,  like  the  ameba,  there  seems  to 
be  a  flow  of  fluid  within  the  body,  but  no  part  of  the  body 
is  set  aside  for  the  purpose. 

315.   History  of  the  knowledge  of  the  circulation.  —  The 

ancients  thought  the  heart  was  the  seat  of  life,  because  the  heart  was 
seen  to  be  the  first  organ  formed  in  an  egg  which  was  being  hatched. 
The  idea  was  confirmed  to  them  by  the  heart's  constant  action,  which 
they  thought  was  caused  by  the  boiling  of  the  animal  spirits.  The 
spirits  then  flowed  away  in  a  sluggish  stream  through  the  veins,  and 
were  not  supposed  to  return  to  the  heart. 

They  concluded  that  the  arteries  carried  only  air,  because  they  always 
found  them  empty  after  death.  They  knew  nothing  whatever  of  the 
capillaries.  They  thought  that  food  was  carried  to  the  liver  and  was 
there  partly  cooked,  and  was  then  sent  on  to  the  heart  where  it  was 
cooked  still  further  in  the  heart's  vital  flame,  until  it  was  turned  to 
blood.  Then  it  was  sent  out  by  way  of  the  veins  to  irrigate  the  body. 
The  valves  of  the  veins  were  supposed  to  oppose  its  flow  and  to  render 
it  sluggish.  The  boiling  in  the  heart  was  supposed  to  heave  the  chest 
up  and  down,  and  cause  air  to  rush  in  and  prevent  too  great  a  degree 
of  heat.  The  brain  also  was  supposed  to  cool  the  blood.  Because  of 
its  more  violent  action  during  physical  exertion  or  emotion,  they  con- 
cluded that  the  heart,  instead  of  the  brain,  was  the  seat  of  the  mind 
and  feelings.  We  still  use  the  v;ord  /learl  with  this  meaning  in  such 
expressions  as  kind-hearted  2,n^  free-hearted. 

Incredibly  few  discoveries  were  made  for  thousands  of  years,  for 
until  within  two  hundred  years  the  law  forbade  any  one  to  dissect  a 
human  body.  In  1628  a  true  explanation  of  the  heart  and  the  course 
of  the  blood  was  first  published  by  Harvey,  an  English  physician. 
The  only  point  which  he  omitted  was  the  explanation  of  how  the  blood 
gets  from  the  arteries  to  the  veins.  Three  years  after  his  death  micro- 
scopes were  made  powerful  enough  to  reveal  the  capillaries  for  the 
first  time,  and  thus  the  truth  of  our  present  ideas  concerning  the  cir- 
culation was  fully  established. 


1 82  APPLIED   PHYSIOLOGY 


SUMMARY 


1.  The   tubes   carrying   blood   away  from   the  heart  are 

called  arteries.  They  are  thick-walled  and  elastic, 
and  in  them  the  blood  is  under  considerable  pressure. 
Each  heart  beat  causes  a  perceptible  wave  in  the 
artery,  which  is  called  the  pitlse. 

2.  The    arteries   divide    and    finally   break   up    into    fine 

tubes  called  capillaries,  which  touch  each  cell  of  the 
body. 

3.  In  the  capillaries  some  of  the  plasma  passes  outside  the 

tubes  and  bathes  the  cells  in  nourishment.  Some  of 
the  oxygen  leaves  the  red  blood  corpuscles  to  go  to 
the  cells  of  the  body.  Some  carbonic  acid  gas  also 
leaves  the  cells  of  the  body  and  combines  with  the 
plasma  within  the  capillary. 

4.  The  capillaries  join  together  to  form  thin-walled  vessels 

called  veins,  which  return  the  blood  to  the  heart. 

5.  The   plasma  which    has   left   the  capillaries   is  called 

lymph.  It  is  returned  to  the  blood  by  means  of  a 
set  of  fine  tubes  called  lymphatics. 

6.  The  lymphatics  unite  to  form  a  tube  called  the  thoracic 

duct,  which  runs  up  the  backbone  and  opens  into  a 
vein  at  the  root  of  the  neck. 

7.  The  right  side  of  the  heart  sends  the  venous  blood  to 

the  lungs,  where  it  passes  through  the  capillaries 
and  is  freed  from  its  impurities,  and  then  returned  to 
the  left  side  of  the  heart  as  arterial  blood  ready  for 
another  circuit  of  the  body.  This  is  called  the  ptd- 
m.onary  circulation. 

8.  The  venous  blood  from  the  stomach  and  intestine  passes 

through  a  second  set  of  capillaries  in  the  liver.  This 
is  called  the  portal  circulation. 


THE   FLOW  OF   BLOOD   IN   THE   BODY  183 


DEMONSTRATIONS 

73.  The  flow  of  blood  in  the  veins  and  the  action  of  the  valves  of 
the  vein  can  be  shown  by  placing  a  finger  upon  a  vein  in  the  skin  upon 
the  back  of  the  hand.  Then  press  out  the  blood  by  running  another 
finger  a  few  inches  up  the  vein.  When  the  second  finger  is  removed, 
notice  that  the  blood  does  not  return  in  the  vein,  for  the  valves  stop 
the  backward  flow ;  but  if  the  first  finger  is  removed,  the  vein  at  once 
fills  up.  This  is  one  of  the  proofs  which  Harvey  used  to  prove  the 
circulation  of  the  blood. 

74.  The  position  of  the  main  arteries  upon  the  limbs  should  be 
shown  upon  the  body.  Remember  that  they  are  usually  over  the  middle 
of  a  joint  upon  the  side  toward  which  it  can  be  bent.  Explain  that 
wherever  a  beating  can  be  felt  there  is  a  pulse  and  an  artery. 

75.  Examine  an  artery  and  vein  prepared  for  the  microscope.  Notice 
its  smooth  and  thin  inner  layer  puckered  because  of  the  contraction  of 
its  outer  coats.  Next  is  the  muscular  layer,  each  cell  wrapped  around 
the  tube.  The  next  and  outermost  layer  is  composed  of  connective 
tissue.  Notice  that  the  main  difference  between  the  arterv'  and  the 
vein  is  that  the  artery  is  thicker. 

76.  Tie  a  string  or  a  rubber  band  rather  tightly  around  the  finger. 
Notice  that  in  a  few  minutes  the  finger  becomes  purple,  cold,  swollen, 
and  painful.  Explain  that  the  string  does  not  exert  enough  pressure 
to  close  the  thick  arteries  which  are  under  high  pressure,  but  that  it 
readily  closes  the  veins. 

']'] .  Show  the  capillary  circulation  in  a  frog's  foot.  Place  the  frog 
in  a  covered  glass  of  water  to  which  a  teaspoonful  of  ether  has  been 
added.  When  it  ceases  to  move,  spread  its  web  over  a  hole  cut  in  card- 
board. A  ring  of  dried  mucilage  will  hold  it  in  place.  Examine  it 
under  a  microscope  with  a  magnifying  power  of  about  200  diameters. 
Oval  cells  will  be  seen  shooting  through  a  network  of  capillaries.  The 
tail  of  a  small  fish  also  will  show  the  circulation. 


REVIEW  TOPICS 

Describe  the  tubes  which  conduct  blood  to  the  cells 
of  the  body,  their  structure,  situation,  arrangement, 
action,  and  pulse. 


1 84  APPLIED   PHYSIOLOGY 

2.  Describe  the  capillaries,  their  structure,  and  action  in 

regard  to  nutrition  and  respiration. 

3.  Describe  the  veijis,  their  structure  and  action. 

4.  Describe  the  pulmonary  circulation  and  the  portal  cir- 

culation. 

5.  Give  the  time  required  for  a  drop  of  blood  to  make  the 

complete  round  of  the  circulation. 

6.  Describe  the  lymph,  the  lymphatics,  the  flow  of  lymph, 

and  the  use  of  lymph. 

7.  Describe  lymph  nodes  and  give  their  use. 

8.  Describe  the  circulation  in  reptiles  and  toads,  in  fishes, 

in  insects,  in  shellfish,  in  the  ameba. 

9.  Give  an  outline  of  ancient  ideas  concerning  the  circula- 

tion of  the  blood,  and  tell  when  and  by  whom  the 
true  circulation  was  discovered. 


CHAPTER   XXI 
REGULATION   OF   THE  FLOW   OF  BLOOD 

316.  Vaso-motor  nerves.  —  The  muscles  in  the  walls  of 
the  smaller  arteries  regulate  the  amount  of  blood  passing 
through  them.  A  special  set  of  nerves,  called  vaso-moior 
nerves,  causes  the  arteries  to  contract.  When  these  nerves 
are  paralyzed,  the  muscles  relax,  and  the  artery  becomes 
fully  distended  by  the  pressure  of  the  blood.  When  any 
part  of  the  body  is  working,  its  arteries  dilate  in  order 
to  supply  a  greater  amount  of  blood  to  the  part. 

The  vaso-motor  nerves  are  affected  by  influences  from 
the  brain.  Embarrassment  and  bashfulness  paralyze  those 
of  the  head,  so  that  more  blood  goes  to  the  face  and  it 
becomes  redder,  or  blushes.  On  the  other  hand,  fear  and 
grief  stimulate  the  nerves  and  cause  a  contraction  of  the 
arteries,  which  drives  the  blood  from  the  face  so  that  pale- 
ness results.  Heat  applied  to  the  skin  causes  the  arteries 
to  dilate,  and  thus  to  contain  more  blood. 

317.  Congestion.  —  More  than  the  natural  quantity  of  blood  re- 
maining in  a  part  for  some  time  is  called  co7igestion.  It  is  liable  to 
injure  the  cells.  Cold  causes  the  arteries  of  the  skin  to  contract  so 
that  less  blood  can  pass  through  them.  The  blood  intended  for  the 
skin  is  thus  directed  through  the  deeper  arteries  which  already  contain 
their  full  amount  of  blood.  So  congestion  of  the  deeper  parts  often 
results.     In  this  way  we  get  cold  in  our  throats. 

318.  Secondary  effects  of  heat  and  cold.  —  When  heat  has 
acted  upon  the  skin  for  some  time  it  causes  a  contraction  of  the  blood 
tubes.      When  first  put  into  a  tub  a  washerwoman's  hands  become 

i8s 


1 86 


APPLIED   PHYSIOLOGY 


red,  but  in  a  few  moments  they  become  white  and  shriveled  from  the 
contraction  of  the  arteries. 

When  cold  has  acted  upon  the  arteries  for  some  time  it  paralyzes 
them  so  that  they  dilate.  When  a  boy  begins  to  snowball,  his  hands 
are  cold,  but  after  a  while  his  hands  glow  with  redness  and  warmth 
because  the  paralyzed  tubes  admit  more  warm  blood. 


319.  Effects  of  injury  upon  the  arteries.  —  When  injured 
in  any  way,  the  injured  part  becomes  red  and  warmer. 
This  is  because  the  same  cause  which  produces  the  injuries 
also  partly  paralyzes  the  smaller  arteries,  so  that  they  dilate 
and  bring  an  extra  quantity  of  blood  for  the  repair  of  the 
wounded  part.  Here,  as  elsewhere,  nature  wonderfully 
adapts  the  body  to  its  surroundings. 

320.  Nature's  arrest  of  hemorrhage.  —  Cut  capillaries 
cause  only  an  oozing  of  blood  which  collects  Uke  drops  of 

dew  over  the  whole  cut 
ct  surface.  Blood  does  not 
spurt  from  a  cut  vein,  but 
wells  out  in  a  slow  stream. 
When  an  artery  is  cut,  the 
blood  flows  in  a  strong  jet. 
Bleeding  from  either  of  the 
vessels  usually  stops  in  a 
few  moments.  The  mus- 
cles of  the  blood  tube 
contract  and  lessen  the 
size  of  the  tube,  or  even 
entirely  shut  it  up ;  the  blood  also  clots  in  the  cut,  and  a 
small  plug  of  clot  extends  into  the  end  of  the  blood  tube. 
In  these  two  ways  bleeding  from  small  cuts  is  soon  stopped 
naturally.  But  in  a  large  artery  the  blood  pressure  is  so 
great  that  it  forces  away  the  clot  as  fast  as  it  is  formed, 
so  that  bleeding  may  continue  until  death  occurs. 


Diagram  of  a  bleeding  cut. 

a   upper  edge  of  a  cut. 
b    a  cut  blood  tube. 


REGULATION  OF  THE  FLOW  OF  BLOOD 


187 


Natural  stoppage  of  bleeding. 

a  upper  edge  of  a  cut. 

b   blood  tube,   showing  its   contracted   cut 

end  filled  with  a  clot, 
c   blood  clot. 


321.  How  to  stop  a  bleeding.  —  It  should  be  remembered 
that  sufficient  pressure  will  instantly  stop  any  bleeding. 
If  a  hand  is  placed  on  each 

side  of  the  cut,  so  as  to  — jzr- ^  "%^    — —     — a- 

hold  its  edges  firmly  to- 
gether, no  bleeding  can 
occur.  A  second  way  of 
stopping  bleeding  is  by 
pressing  a  handkerchief, 
or  a  finger,  or  even  the 
whole  hand,  into  the 
wound.  A  third  way  in 
which  bleeding  may  be 
stopped  is  by  cutting  off 
the  supply  of  blood  to  the  part.  This  may  be  done  by 
tying  a  handkerchief  very  tightly  around  the  limb  be- 
tween the  wound  and  the  heart.  The  knot  in  the  hand- 
kerchief should  lie  over  the  artery,  and,  if  necessary,  a 
stick  may  be  inserted  under  the  band  and  twisted  tightly. 
Of  these  three  ways  of  stopping  bleeding,  that  of  compres- 
sion by  the  hands  is  the  best  to  use  at  first. 

322.  Position  of  arteries.  —  Main  arteries  run  in  a  general 
direction  down  the  middle  of  each  limb,  upon  the  side  on  which  the 
limb  can  be  bent.  Thus  in  the  upper  part  of  the  arm,  the  artery  runs 
across  the  center  of  the  armpit,  and  then  dow-n  the  inner  side  of  the 
upper  arm.  At  the  elbow  it  lies  in  the  center  of  the  front  side  of  the 
arm.  An  artery  lies  upon  the  thumb  side,  and  another  upon  the  little 
finger  side  of  the  front  of  the  wrist. 

In  the  leg  the  main  artery  lies  in  the  middle  of  its  upper  part,  and 
reappears  at  the  surface  in  the  middle  of  the  bend  of  the  knee.  At  the 
ankle  it  is  divided  into  two,  one  of  which  is  just  behind  the  inner  ankle 
bone,  and  the  other  runs  down  the  middle  of  the  front  of  the  foot. 

There  is  a  large  artery  and  a  large  vein  in  the  middle  of  each  side 
of  the  neck.  These  positions  should  be  remembered,  for  they  are  the 
principal  places  in  which  a  large  blood  tube  is  likely  to  be  wounded, 


i8S 


APPLIED   PHYSIOLOGY 


and  they  mark  the  course  of  the  tubes  in  case  they  should  need  to  be 
compressed  to  stop  bleeding. 

323.  Repair  of  wounded  tubes.  —  When  a  vein  is  cut 
in  two,  its  ends  may  grow  together  again,  but  when  an 
artery  is  cut,  each  end  of  the  tube  remains  permanently 


■x 


The  left  upper  arm. 

The  dotted  line  indicates  the 
course  of  the  main  artery  (the 
brachial). 


The  right  thigh. 

The  dotted  line  indicates  the 
course  of  the  main  artery  (the 
femoral). 


closed,  and  thus  the  supply  of  blood  to  the  part  is  at  least 
partly  cut  off.  Branches  from  an  artery  communicate 
with  other  branches  which  begin  a  few  inches  further 
down  the  same  artery.  When  the  artery  is  cut,  these 
communicating  branches  enlarge,  and  thus  permit  the 
natural  amount  of  blood  to  flow  around   the  wound  and 


REGULATION  OF  THE  FLOW  OF  BLOOD      1 89 

SO  reach  the  artery  below  the  cut.     When  capillaries  are 
cut,  a  new  set  is  produced  to  take  their  place. 

324.  Effect  of  tight  bands.  —  A  tight  band  will  obstruct  the 
flow  of  blood  in  the  veins,  while,  unless  it  is  very  tight,  it  scarcely 
affects  the  arteries.  So  the  blood  freely  enters  a  part  through  the 
arteries,  but  is  held  back  in  the  veins  below  the  band,  until  the  part  is 
distended  with  blood,  and  the  proper  amount  of  new  arterial  blood  is 
prevented  from  entering.  As  a  result  the  nutrition  of  the  part  suffers 
and  slight  injuries  do  not  heal  readily.  The  veins  swell  from  the  extra 
amount  of  blood  they  contain,  and  finally  enlarge  in  places,  forming 
what  are  called  varicose  veins.  Tight  garters  are  common  offenders  in 
this  respect. 

325.  Alcohol  and  arteries. — When  a  cup  of  hot  coffee 
is  swallowed,  the  temperature  of  the  stomach  and  of  the 
blood  in  its  walls  is  raised.  Then  nature  at  once  causes 
the  arteries  of  the  skin  to  become  enlarged  so  that  more 
blood  may  come  in  contact  with  the  cool  air,  and  thus  give 
off  the  surplus  heat.  Probably  in  the  same  manner  the  heat 
produced  by  the  destruction  of  alcohol  causes  the  arteries  of 
the  skin  to  dilate  so  that  they  contain  an  excess  of  blood. 
A  red  face  and  nose  are  well-known  signs  of  drinking. 
This  dilation  of  the  arteries  is  one  of  the  most  marked 
and  constant  effects  of  drinking. 

326.  Alcohol  and  the  nutrition  of  cells.  —  Naturally, 
when  a  part  of  the  body  is  at  work,  its  blood  tubes 
become  larger,  while  those  of  the  resting  parts  become 
smaller.  If  the  blood  tubes  of  distant  parts  remain  large, 
there  will  not  be  suf^cient  blood  to  fill  those  of  the  work- 
ing part,  and  thus  the  part  will  not  be  able  to  put  forth  its 
full  strength.  If  a  part  is  injured,  it  cannot  get  enough 
extra  blood  to  repair  itself  quickly.  Thus  wounds  will  be 
apt  to  heal  slowly,  while  inflammation  will  be  more  likely 
to  set  in. 


1 90  APPLIED    PHYSIOLOGY 

If  a  part  is  continuously  supplied  with  an  excess  of 
blood  by  dilated  arteries,  there  is  apt  to  be  an  overgrowth 
of  some  of  its  tissues,  especially  of  connective  tissue.  An 
excess  of  this  tissue  interferes  with  the  action  of  the  work- 
ing cells  of  the  part.  This  change  is  apt  to  occur  especially 
in  the  arteries  themselves,  making  them  thick  and  hard. 
It  naturally  comes  on  during  old  age,  but  is  often  hastened 
by  the  use  of  strong  drink.  The  affected  arteries  cannot 
change  their  size,  and  so  the  parts  which  they  supply 
suffer  in  nutrition.  Although  an  excess  of  blood  may  go 
to  a  part,  yet  it  is  not  renewed  so  often  as  it  should  be. 

SUMMARY 

1.  The  muscles  in  the  arteries  give  them  the  power  of 

becoming  smaller  or  larger  in  order  to  regulate  the 
amount  of  blood  going  to  any  part  of  the  body. 

2.  The  contraction  and  relaxation  of  the  arteries  is  con- 

trolled by  a  set  of  nerves  called  vaso-motor  nerves. 

3.  Heat,  cold,  work,  and  mental  influences  are  a  few  causes 

which  excite  the  action  of  the  arterial  muscles. 

4.  Contraction  of  arteries  near  the  surface  and  dilatation 

of  the  deeper  ones  is  the  common  cause  of  taking 
cold. 

5.  Alcohol  causes  a  paralysis  of  the  muscles  of  the  arteries 

so  that  they  may  remain  permanently  enlarged.    The 
arteries  of  the  face  and  stomach  are  most  affected. 

6.  Small  blood  tubes,  when  cut,  bleed  for  a  moment  until 

the  ends  of  the  tubes  contract  and  a  clot  plugs  them 
up  completely. 

7.  Large    blood    tubes    may    bleed    until    death    occurs. 

Bleeding   can   always   be   stopped  by   grasping  the 
part  boldly  and  firmly. 


REGULATION   OF  THE   FLOW  OF  BLOOD  191 

8.  Large    blood    tubes  run  down  the  middle  of  the  limb 

upon  the  side  toward  which  the  limbs  are  bent. 

9,  Tight  bands  obstruct  the  flow  of  blood  going  from  a 

limb,  but   permit   blood   to   enter.     Thus   the   limb 
swells  and  the  veins  enlarge. 

DEMONSTRATIONS 

78.  The  effect  of  injury  upon  the  arteries  can  be  illustrated  by  scratch- 
ing the  arm  with  the  point  of  a  pin.  In  a  few  seconds  a  bright  red 
mark  appears  in  its  track. 

79.  Hold  the  hand  in  a  basin  of  hot  water.  Notice  that  at  first  the 
skin  is  red  from  the  dilatation  of  the  arteries.  In  course  of  ten  min- 
utes the  skin  becomes  white  and  puckered,  because  heat  has  a  second 
effect  of  contracting  arteries. 

80.  Show  how  bleeding  can  be  stopped,  by  boldly  grasping  an  imag- 
inary cut  and  holding  its  edges  tightly  together.  Show  how  a  band 
can  be  tied  loosely  around  a  limb  above  a  cut,  and  then  by  means  of  a 
stick  inserted  under  the  band,  can  be  twisted  as  tightly  as  one  pleases 
so  as  to  control  bleeding. 

REVIEW  TOPICS 

1.  Describe  vaso-motor  nerves. 

2.  Show  how  vaso-motor  nerves  are  affected  by  influences 

from  the  brain ;  by  heat  and  cold  ;  by  injuries. 

3.  Describe  congestion  and  how  it  is  caused  by  cold. 

4.  Give  the  effects  of  alcohol  upon  the  contraction   and 

dilatation  of  the  arteries. 

5.  Give   the    difference    between    arterial,   capillary,    and 

venous  bleeding. 

6.  Describe  how  bleeding  naturally  stops. 

7.  Describe  three  ways  of  stopping  bleeding. 

8.  Describe  how  nature  restores  the  circulation  after  an 

artery  is  cut  in  two ;  after  a  vein  is  cut ;  and  after 
capillaries  are  cut. 

9.  Give  the  effect  of  tight  bands  upon  the  circulation  of  a 

limb. 


CHAPTER   XXII 

THE  LUNGS 

327.  Oxidation.  —  Life  is  a  process  of  oxidation.  The 
body  is  an  engine.  The  living  cells  are  the  machinery, 
and  both  they  and  the  blood  are  the  fuel.  The  fires  are 
lighted  at  birth,  and  burn  without  cessation  until  death. 

328.  Respiration.  —  In  every  fire  a  free  draft  of  air  must 
be  supplied  and  the  burned  products  must  be  carried  off. 
So  in  the  body  air  must  enter  continually,  and  the  oxidized 
products  pass  out  again.  The  red  blood  cells  are  set  apart 
for  the  special  work  of  carrying  oxygen  to  the  rest  of  the 
cells  of  the  body,  while  the  lungs  are  arrangements  in 
which  the  red  blood  cells  can  obtain  oxygen  from  the  air. 
The  passage  of  air  into  and  out  of  the  lungs  is  breathing. 
Breathing  and  oxidation  together  constitute  respiration. 

329.  Respiratory  organs.  —  An  air  tube  leads  from  the 
surface  of  the  body  to  the  lungs.  The  parts  of  the  tube 
from  the  surface  to  the  lungs  are  the  nose^  pharynXy  larynx^ 
trachea,  and  bronchi.  These  parts  taken  together  form  the 
respiratory  tract.  They,  together  with  the  lungs  and  red 
blood  cells,  form  the  respiratory  system. 

330.  The  nose. — The  nose  is  a  double  tube  lined  with 
mucous  membrane.  Each  tube  has  a  smooth  bottom  and 
inner  wall,  but  its  outer  wall  is  thrown  into  three  curved 
folds  extending  lengthwise  so  as  almost  to  form  partitions 
across  the  tubes.  The  folds  warm  the  air  and  strain  out 
dust  as  it  passes  over  their  surfaces.     From  each  side  of 

192 


THE   LUNGS  193 

the  nose  a  tube  extends  to  the  eye  to  drain  away  tears,  and 
another  opening  extends  into  the  anUnim  or  cavity  in  the 
upper  jawbone.  In  the  nose  there  are  special  nerves  of 
the  sense  of  smell.      (See  p.  324.) 

331.  The  pharynx.  —  The  pharynx  is  the  muscular  bag 
just  back  of  the  mouth,  through  which  both  food  and  air 
pass.  Air  should  always  enter  it  from  the  nose.  Just  in 
front  of  the  pharynx  upon  each  side  is  a  fleshy  body,  look- 
ing like  an  almond,  and  called  the  tojisil.  Sometimes  the 
tonsils  become  very  large  in  children  and  close  the  open- 
ing into  the  nose,  making  it  necessary  to  breathe  through 
the  mouth. 

332.  Adenoid  vegetations. —  In  the  upper  part  of  the 
pharynx,  just  behind  the  opening  of  the  nose,  there  often 
grows  a  collection  of  soft,  grapelike  bodies,  called  ade- 
noid  vegetations.  They  close  the  opening  to  the  nose  and 
compel  a  person  to  breathe  through  the  mouth.  They 
begin  to  form  during  early  childhood  while  the  bones  are 
growing.  The  unnatural  breathing  and  open  mouth  de- 
form the  upper  jaw  so  that  it  becomes  narrow  and  pointed. 
The  trouble  is  a  serious  one.  While  it  does  not  cause 
inconvenience  in  itself,  yet  it  compels  mouth  breathing; 
it  renders  the  child  very  susceptible  to  taking  cold ;  and 
is  the  most  common  cause  of  deafness,  for  it  stops  the 
Eustachian  tube  leading  to  the  ear.  Often  they  are  asso- 
ciated with  large  tonsils. 

When  a  child  becomes  grown,  the  adenoid  vegetations 
often  shrink,  and  so  cure  themselves,  but  the  deformed  jaw 
lasts  through  life.  They  can  easily  be  broken  down  and 
removed  with  the  finger,  as  they  should  be  in  every  case. 

333.  Mouth  breathing.  —  The  mouth  contains  no  means  for 
warming  the  air,  or  for  screening  out  dust  and  disease  germs,  as  the 
nose  has.     So  a  mouth  breather  is  very  likely  to  take  cold.     When  he 

ov.  PHYSIOL.  —  13 


194 


APPLIED   PHYSIOLOGY 


makes  an  extra  exertion  and  becomes  short  of  breath,  the  air  irritates 
the  throat  and  brings  on  a  cough. 

With  many,  mouth  breathing  is  a  habit  which  can  easily  be  broken 
by  attention  to  the  breathing.  In  others,  it  is  due  to  a  cold,  or  to  ade- 
noid vegetations,  or  to  enlarged  tonsils. 

334.  The  larynx.  — In  the  front  side  of  the  lower  part 
of  the  pharynx  is  the  opening  of  a  box  called  the  larynx^ 
through  which  air  passes.     The  larynx  is  a  box  of  carti- 


A  slice  from  the  trachea  (x  200). 

a  cartilage.  b  glands  in  the  mucous  membrane. 

c    lining  of  epithelial  cells, 

d  cilia  upon  the  surface  of  the  epithelium. 

lage.  Across  its  upper  end  are  stretched  two  thin  elastic 
bands,  the  vocal  cords,  which  can  be  tightened  and  brought 
near  together  at  will.  Air  passing  between  them  produces 
a  sound  called  the  voice. 

335.  The  trachea.  —  From  the  bottom  of  the  larynx 
there  extends  downward  a  tube  called  the  windpipe  or 
trachea.  The  trachea  is  about  four  and  one  half  inches 
in  length  and  three  quarters  of  an  inch  in  diameter.  It 
is  composed  of  a  framework  of  twenty  hoops  of  cartilage, 


THE   LUNGS 


195 


bound  together  with  tough  connective  tissue  and  lined  with 
mucous  membrane. 

336.  The  bronchi.  —  Within  the  chest  the  trachea  divides 
into  two  tubes,  the  bronchi.  Each  bronchus  divides  again 
and  again,  until  the  finest 
divisions  are  about  ^^ 
inch  in  diameter.  Like 
the  trachea,  each  bron- 
chus is  composed  of  hoops 
of  cartilage  lined  with 
mucous  membrane. 

337.  Cilia.  — The  sur- 
face of  the  epithelium  of 
the  mucous  membrane  of 
most  of  the  nose  and 
larynx  and  the  whole  of 
the  trachea  and  bronchi 
is  covered  with  micro- 
scopic hairs,  the  cilia. 
Each  cilium  is  slightly 
curved  upward  and  waves 
continually  in  a  rapid  up 
and  down  motion  which 
tends   to  force   dust  and 

away    from     the 


L/lllll|||<1')ffi5 


Diagram  of  trachea  and  bronchi. 

a   larynx.  b   trachea.  c   bronchi. 

d  air  sacs  of  the  lung. 


mucus 
lungs. 

338.  The  lungs.  — The  ends  of  the  bronchi  are  studded 
with  numerous  cup-shaped  depressions  called  air  sacs,  each 
about  Y^  inch  in  diameter.  Upon  the  inner  surface  of 
each  air  sac  is  a  close  network  of  capillary  blood  tubes. 
The  collection  of  bronchi,  air  sacs,  and  blood  tubes  forms 
two  spongy  bodies  called  lungs.  Between  the  air  sacs 
is  a  thin  layer  of    connective  tissue.     The  lungs' can  be 


196 


APPLIED   PHYSIOLOGY 


Stretched  like  rubber  bags,  when  air  is  blown  through  the 
trachea,  and  will  contract  to  their  former  size  when  the  air 
has  been  let  out. 

339.  The  chest  or  thorax.  —  The  lungs  are  covered  by 
the  ribs,  which  are  hinged  to  the  spinal  column  behind, 
and  to  the  breastbone  in  front,  so  as  to  form  a  bony  frame- 


Diagram  of  the  air  sacs  in  a  man's  lung. 

a  smallest  bronchial  tube. 

d   a  collection  of  air  sacs  cut  lengthwise. 

c   air  sacs  cut  across. 

d  connective  tissue  between  the  air  sacs. 


Diagram  of  a  frog's 
lung. 


work  inclosing  a  cavity  called  the  ckesf  or  thorax.  The 
floor  of  the  thorax  is  formed  by  a  muscle  called  the 
diaphragm,  which  is  attached  to  the  lower  border  of  the 
ribs,  and  arches  upward.  It  is  lined  with  a  smooth  and 
shining  serous  membrane  like  peritoneum,  called  the 
pleura.     Each  lung  is  covered  with  pleura  also. 

340.  Inspiration  and  expiration.  —  Muscles  connect  and 
cover  the  ribs.  They  raise  the  ribs  and  expand  the  chest. 
The   diaphragm   flattens   its   arch    and    makes   the  chest 


THE   LUNGS  1 97 

deeper.  Thus  the  size  of  the  chest  can  be  increased  in 
all  directions.  When  the  chest  expands,  air  rushes  in 
to  distend  the  lungs.  The  entrance  of  air  into  the  lungs 
is  called  mspiratiofi.  At  the  end  of  inspiration  the 
muscles  relax.  Then  the  weight  of  the  parts  and  the 
elasticity  of  the  distended  lung  forces  out  the  air.  In 
addition,  the  muscles  of  the  abdomen  and  arms  can  be 
made  to  contract  so  as  to  expel  the  air  with  greater  force. 
Driving  out  the  air  from  the  lungs  is  called  expiration. 

341.  Amount  of  expansion. — In  an  ordinary  inspiration  the 
chest  becomes  from  one  half  an  inch  to  one  inch  larger  around.  By 
taking  a  very  deep  breath  most  people  can  expand  the  chest  two  or 
three  inches.  An  expansion  of  four  or  five  inches  is  exceptional.  By 
breathing  exercises  the  expansion  can  be  increased. 

342.  Amount  of  air  used  in  each  breath.  —  After  the 
fullest  possible  inspiration,  the  lungs  contain  about  330 
cubic  inches  of  air.  After  the  fullest  possible  expiration, 
the  lungs  still  contain  about  100  cubic  inches  of  air.  So  it 
is  possible,  by  strong  effort,  to  inhale  and  exhale  about 
230  cubic  inches  of  air.  This  is  called  the  vital  capacity 
of  the  lungs,  and  is  the  breathing  power  which  can  be 
used  in  violent  exercise.  But  in  quiet  breathing  only 
about  30  cubic  inches  of  air  are  inhaled.  This  is  called 
tidal -dxx.  By  an  effort  about  100  cubic  inches  of  air  can 
be  inhaled  in  addition  to  the  tidal  air.  This  is  called  the 
coinplei}iental  air.  By  a  forced  expiration,  the  lungs  can 
expel  about  100  cubic  inches  of  air  more  than  in  quiet 
breathing.  This  is  called  the  reserve  or  supplemental  air. 
There  still  will  be  left  100  cubic  inches  of  air,  called 
residual  air. 

343.  Action  of  the  cilia.  —  The  motion  of  the  cilia  creates 
an  air  current  in  the  smaller  bronchi,  which  mixes  the  in- 
coming fresh  air  with  that  already  in  the  lungs,  so  that 


198  APPLIED    PHYSIOLOGY 

while  all  the  air  is  not  changed  with  each  inspiration,  yet 
there  is  a  free  mingling  of  the  fresh  with  the  impure  air. 
The  cilia  also  intercept  particles  of  dust  which  the  nose 
and  pharynx  have  failed  to  remove. 

344.  Rate  of  breathing.  —  In  health  an  inspiration  occurs 
with  every  four  heart  beats,  or  about  eighteen  times  each 
minute,  but  in  exercise  its  rate  may  be  increased  to  sixty 
or  seventy  times  a  minute.  A  baby  breathes  about  forty 
times  a  minute.  The  rate  slowly  diminishes  until,  at 
eighteen  years  of  age,  it  is  the  same  as  in  a  man. 

An  inspiration  takes  about  five  sixths  as  long  as  expira- 
tion, but  the  regularity  and  force  of  both  inspiration  and 
expiration  can  be  varied  indefinitely.  Respiration  usually 
goes  on  without  a  person's  knowledge  or  thought,  yet  it  is 
somewhat  under  the  control  of  the  will  in  talking,  blow- 
ing, and  other  actions. 

345.  Modifications  of  breathing.  —  Coughing  x?,  a  forcible  expi- 
ration in  which  the  closed  vocal  cords  are  suddenly  blown  open  with 
force. 

Sneezing  is  a  sudden  expiration  in  which  air  is  driven  mainly  through 
the  nose. 

Blowing  IS  a  long  forcible  expiration  in  which  air  is  forced  in  a  steady 
stream  through  a  small  opening  in  the  lips. 

Laughing  and  crying  are  each  a  succession  of  short  expirations. 
They  sound  so  much  alike  that  it  is  often  impossible  to  tell  which  a 
child  is  doing. 

Sobbing  IS  a  succession  of  short  inspirations. 

Hiccoughing  is  a  single  inspiration  caused  by  a  sudden  contraction  of 
the  diaphragm. 

Snoring  is  a  sound  produced  during  inspiration  by  air  passing  over 
the  soft  palate.  It  is  usually  due  to  air  passing  through  both  the  nose 
and  the  mouth  at  the  .same  time. 

Gapi?ig  or  yawning  is  a  long  and  deep  inspiration  and  expiration 
through  the  open  mouth,  while  the  muscles  of  the  throat  are  strongly 
contracted. 


THE   LUNGS  1 99 

Sighing  is  a  deep  inspiration  followed  by  a  sudden  relaxation  of  the 
muscles  so  that  the  escaping  air  makes  a  sound. 

Choking  is  a  sudden  stoppage  of  the  larynx  or  trachea.  When  a 
person  is  choked,  he  should  he  down  upon  his  face  with  his  head 
lowest.  Slapping  his  back  will  aid  in  jarring  the  substance  loose. 
If  this  does  not  dislodge  it,  he  should  be  hung  head  downwards  while 
his  back  is  pounded  vigorously.  In  that  position  the  substance  may 
fall  out,  while  if  he  sits  upright,  it  may  fall  in  deeper  unless  it  is  coughed 
out. 

Suffocation,  or  smothering,  is  a  cessation  of  breathing  caused  by 
shutting  off  the  air  either  partly  or  wholly. 

Siickijig  is  an  inspiratory  act,  done  by  depressing  the  floor  of  the 
mouth  so  as  to  form  an  empty  space  into  which  anything  held  between 
the  lips  is  forced  by  the  pressure  of  the  air. 

Spitting  is  an  expiratory  act  in  which  the  lips  are  blown  open  with 
an  explosive  noise.     It  can  be  done  by  the  mouth  alone. 

346.  Breathing  sounds.  —  In  natural  breathing,  air  rush- 
ing in  and  out  of  the  lungs  produces  a  low,  blowing  sound, 
distinct  from  the  sound  made  by  the  breathing  in  the  nose 
and  throat.  The  sound  of  the  voice,  when  transmitted 
through  the  chest,  has  a  characteristic  quality  and  pro- 
duces a  vibration  of  the  chest  walls.  When  the  chest  is 
struck  with  the  finger,  the  sound  is  modified  by  the  reso- 
nant quality  of  the  lungs.  All  these  sounds  are  changed 
in  lung  diseases,  and  give  a  sure  indication  of  the  nature 
and  extent  of  the  disease. 

347.  Abdominal  and  thoracic  breathing.  —  When  the  dia- 
phragm contracts,  it  forces  the  abdominal  organs  down- 
ward, making  the  abdomen  more  prominent.  Breathing 
by  the  free  use  of  the  diaphragm  is  called  abdominal 
breathing.  When  the  diaphragm  remains  comparatively 
quiet,  the  ribs  are  compelled  to  move  more  freely.  Breath- 
ing mainly  by  use  of  the  ribs  is  called  thoracic  breathing. 
In  men  abdominal  breathing  is  greatest,  while  in  women 
thoracic  breathing  seems  more  prominent. 


200 


APPLIED   PHYSIOLOGY 


Distention  of  the  stomach  and  intestine  by  a  full  meal, 
or  by  gas,  interferes  with  the  downward  movements  of 
the  diaphragm,  and  compels  a  greater  extent  of  thoracic 
breathing. 


i 


11(0''' 


,„n«i"'W////'//'^' 


\ 


^^'''        'fh.     % 


\\\\\l 


'  Natural  form.  i 

348.  Effect  of  tight  lacing.  —  A  person  whose  waist  is 
laced  tightly  with  corsets  cannot  breathe  in  the  proper 
amount  of  air,  but  is  short  of  breath  and  easily  fatigued. 

Tight  corsets  also  compress  the  liver  and  other  abdomi- 
nal organs.  In  extreme  cases  the  liver  becomes  divided 
almost  into  two  parts  by  the  pressure. 


THE   LUNGS 


20 1 


349.  The  respiratory  center. — The  movements  of  the 
chest  and  diaphragm  in  breathing  are  controlled  by  a 
small  part  of  the  brain  situated  just  above  the  spinal  cord, 
and  called  the  respi7'atory  ceiiter.     When  it  is  destroyed, 


-'I""..... ''I. 


I 


^.y 


Results  of  unhealthful  dress. 


respiration  ceases  at  once,  and  no  power  can    arouse    it 
again. 

Stimulation  of  the  nerves  of  the  body  which  go  to  the  respiratory 
center  may  cause  it  to  send  out  orders  for  the  respiratory  muscles  to 
act.      Thus,  suddenly  throwing  cold  water  on  the  chest  will  cause  a 


202 


APPLIED   PHYSIOLOGY 


contraction  of  the  muscles  of  breathing  which  lasts  for  a  few  seconds, 
so  that  a  person  cannot  catch  his  breath. 

A  substance  sucked  into  the  trachea  irritates  the  nerves  which  go  to 
the  respiratory  center.  The  center  sends  back  an  order  to  the  respira- 
tory muscles  to  expel  the  substance  by  a  forcible  blast  of  air.  Thus 
the  substance  is  coughed  or  sneezed  up. 


350.    Artificial  respiration.  —  The  walls  of  the  chest  are 
elastic  and  quickly  return  to  their  natural  size  when  they 

are  relieved  of 
stress.  It  is  pos- 
sible, therefore,  to 
imitate  natural 
respiratory  move- 
ments upon  a  man 
who  has  stopped 

Diagram  of  artificial  respiration,  showing  inspiration,    breathing.        This 

The  arrows  show  that  the  arms  are  moved  outward        jg   c^Hgd^  avtiUcicil 
from  the  sides  of  the  chest. 

respiration. 
By  pressing  hard  upon  the  chest  fifteen  or  twenty  times 
a  minute,  a  great  deal  of  air  will  be  made  to  pass  in  and 
out  of  the  chest. 
A  more  effective 
method  is  to  lay 
the   person  upon 
his  back,  with  the 
head  lowest  if  pos- 
sible.      Standing 
at  his  head,  draw 
each      arm      out- 
ward and  upward, 
in     a    semicircle, 


f:yp.L^^.Ooj 


Diagram  of  artificial  respiration,  showing  expiration. 
The  arrows  show  that  the  arms  are  carried  directly  for- 
ward until  they  are  pressed  hard  against  the  chest. 


away  from  his  body,  until  they  are  stretched  above  his  head 
almost  in  a  line  with  his  body.     This  raises  the  chest  and 


THE   LUNGS  203 

produces  an  inspiration.  Then  carry  the  arms  directly 
forward  and  down  and  press  them  forcibly  against  the 
side  of  the  chest.  This  produces  an  expiration.  These 
movements  should  be  repeated  about  fifteen  or  twenty 
times  a  minute,  or  at  the  rate  of  natural  breathing. 

If  an  assistant  grasps  the  tongue  and  pulls  it  forward 
during  each  inspiration,  it  will  open  the  larynx  and  also 
stimulate  the  nerves  going  to  the  respiratory  center. 

Every  person  should  know  how  to  perform  artificial 
respiration,  for  it  may  be  the  means  of  saving  a  life  from 
drowning  or  from  an  electric  shock.  No  one  should 
hesitate  to  attempt  artificial  respiration  in  these  cases,  for 
even  crude  and  ignorant  attempts  will  result  in  the  entrance 
of  some  air  and  may  save  a  life. 

SUMMARY 

1.  The  lungs  are  two  organs  from  which  the  red  blood 

cells  obtain  oxygen  for  the  use  of  the  cells  of  the 
body. 

2.  Each  lung  is  made  of  tiny  air  sacs  which  communicate 

freely  with  the  air  through  the  windpipe  and  nose. 

3.  Each  lung  rests  upon  a  curved  muscle  called  the  dia- 

phragjn,  and  is  covered  by  curved  ribs. 

4.  When  the  ribs  are  lifted  or  the  diaphragm  depressed, 

air  enters  the  lungs.     This  is  inspiration. 

5.  When  the  muscles  relax,  the  weight  of  the  parts  and 

the  elasticity  of  the  lungs  drive  out  some  of  the  air. 
This  is  expiration. 

6.  Inspiration    and    expiration    occur    alternately    about 

eighteen  times  a  minute. 

7.  The  movements  of  the  ribs  and  diaphragm  in  breath- 

ing are  controlled  by  a  small  part  of  the  brain  just 
above  the  spinal  cord. 


204  APPLIED   PHYSIOLOGY 

8.  Artificial  respiration  can  be  performed  by  alternately 
pulling  the  arms  above  the  head  and  compressing 
them  against  the  chest  about  twenty  times  a  minute. 

DEMONSTRATIONS 

8i.  Each  pupil  can  notice  the  different  movements  of  his  own 
breathing.  At  will  he  can  change  from  abdominal  breathing  to  thoracic 
breathing,  or  can  use  all  of  the  muscles  of  the  chest  in  taking  a  very 
deep  inspiration.  A  tape  measure  passed  around  the  body  just  under 
the  armpits  will  show  how  the  chest  increases  in  size  with  each  inspira- 
tion and  diminishes  with  expiration. 

82.  A  small  animal  should  be  killed  and  its  chest  opened  so  as  to 
show  the  lungs  and  heart  in  place.  Notice  the  shining  pleura,  and 
that  at  the  back  part  of  the  chest  it  leaves  the  chest  wall  and  covers 
the  lungs.  Notice  the  position  of  the  ribs  and  diaphragm,  and  the  ar- 
rangement and  direction  of  their  muscle  fibers.    (See  demonstration  35.) 

83.  In  a  recently  killed  cat  or  dog  the  diaphragm  can  be  made  to 
contract  by  irritation  of  the  nerve  called  the  phretiic  nerve,  which  con- 
veys orders  for  motion  from  the  respiratory  center  to  the  diaphragm. 
There  are  two  nerves,  one  of  which  enters  the  diaphragm  near  the 
middle  of  each  side  of  the  arch.  Remove  the  lungs  carefully.  Then 
the  site  of  the  nerve  can  be  recognized  by  a  slight  roughness  in  the 
otherwise  smooth  pleural  covering.  Pricking  or  pinching  this  point 
will  cause  a  contraction  of  the  diaphragm.     (See  demonstration  35.) 

84.  Kill  a  frog  by  placing  it  in  a  tight  jar  with  a  few  drops  of  chloro- 
form. Open  its  chest  and  abdomen.  Insert  a  small  pointed  glass  tube 
into  its  trachea.  The  slitlike  opening  can  be  found  upon  the  back  of 
the  tongue.  Blow  through  the  tube  to  inflate  the  lungs,  and  at  once  tie 
a  string  tightly  around  their  base.  Remove  the  lungs  and  let  them  dry. 
Notice  the  partitions  like  the  cells  in  a  honeycomb,  extending  a  little 
way  into  the  central  cavity.  Explain  that  a  man's  lung  is  like  a  col- 
lection of  tiny  frog's  lungs.     (See  illustration  on  page  196.) 

85.  Examine  a  prepared  microscopic  specimen  of  a  lung  and  of 
the  trachea  and  bronchi.  Notice  the  ciliated  epithelium  in  the  trachea 
and  bronchi.  Notice  that  the  walls  of  the  air  sacs  form  an  irregular 
network  inclosing  the  large  spaces  of  the  air  sacs.  The  specimen 
will  probably  show  a  small  bronchus.  Notice  its  thick  walls  containing 
some  muscular  tissue  and  possibly  some  cartilage. 


THE  LUNGS  205 

86.  Show  the  class  how  to  perform  artificial  respiration.  Have  a 
boy  lie  upon  a  desk  and  go  through  the  movements  of  carrying  his 
arms  above  his  head  and  of  pressing  them  against  his  side  again.  Do 
not  perform  the  movements  too  rapidly  and  do  not  press  the  arms  too 
far  backward  above  the  head. 

87.  The  pharynx  and  palate  are  puzzling  parts  to  understand,  but 
are  very  simple  when  shown  upon  a  small  animal.  With  a  sharp  knife 
and  fine  saw,  divide  the  head  and  neck  of  a  small  animal  through  the 
middle  of  the  nose  and  backbone.  Show  that  the  hard  palate  and  the 
soft  palate  divide  the  nose  from  the  mouth.  Show  that  the  pharynx 
extends  upward  behind  the  nose  and  downward  lower  than  the  tongue. 
Show  the  position  of  the  tonsils  and  where  adenoid  vegetations  form. 

88.  Cilia  can  be  shown  with  cells  from  a  frog's  mouth.  Gently 
scrape  its  roof,  removing  a  drop  of  slime  with  some  of  the  epithelial 
cells.  Examine  it  with  the  high  power  of  the  microscope.  The  cilia 
will  appear  as  a  fringe  in  rapid  motion.      (See  demonstration  35.) 


REVIEW  TOPICS 


Define  respiratio7i  and  state  its  object. 

Describe  the  nose,  phary7ix,  larynx,  trachea,  bronchi, 
cilia,  air  sacs,  lungs,  2Ci\^  pletn'a. 

Describe  adenoid  vegetations  and  their  effects. 

Give  the  evil  effects  of  month  breatJiing. 

Describe  the  chest,  ribs,  and  diaphragm. 

Describe  inspiration  and  expiration. 

Give  the  amount  of  air  used  in  ordinary  and  in  forced 
breathing. 

Give  the  action  of  the  cilia. 

Give  the  rate  of  breathing,  and  its  variation  in  laugh- 
ing, sobbing,  coughing,  hiccoughing,  sneezing,  gap- 
ing, sighing,  and  snoring. 

10.  Describe  the  sounds  produced  by  breathing. 

11.  Describe  abdominal  and  thoracic  breathing. 

12.  Give  the  effects  of  tight  lacing. 

13.  Describe  the  respiratory  center  and  its  action. 


CHAPTER    XXIII 
RESPIRATION   OF   THE   TISSUES 

351.  Changes  in  respired  air.  —  The  air  is  composed  of 
about  80  per  cent  of  nitrogen,  20  per  cent  of  oxygen,  and 
y-g-Q-  per  cent  of  carbonic  acid  gas.  The  nitrogen  has  no 
effect  upon  the  body,  but  acts  simply  by  dikiting  the  oxy- 
gen. Air  which  is  ordinarily  breathed  out  from  the  lungs 
contains  16  per  cent  of  oxygen  and  4  per  cent  of  carbonic 
acid  gas,  while  the  amount  of  nitrogen  remains  unchanged. 
Thus,  in  breathing,  the  air  gains  as  much  carbonic  acid 
gas  as  it  loses  oxygen.  Expired  air  is  warmer  and  con- 
tains more  watery  vapor  than  inspired  air,  and  sometimes 
contains  a  trace  of  a  very  poisonous  organic  gas. 

352.  Blood  changes  in  the  lungs.  —  Every  100  cubic 
inches  of  venous  blood  entering  the  lungs  contain  46  cubic 
inches  of  carbonic  acid  gas,  and  from  8  to  12  cubic  inches 
of  oxygen  gas.  As  it  leaves  the  lungs  the  same  amount 
of  blood  contains  about  40  cubic  inches  of  carbonic  acid 
gas,  and  20  cubic  inches  of  oxygen  gas,  and  it  has  changed 
its  shade  from  the  dark  red  of  venous  blood  to  the  bright 
red  tint  of  arterial  blood.  It  has  also  lost  a  small  amount 
of  water  and  some  heat.  The  essential  change  which 
occurs  in  the  passage  of  blood  through  the  lungs  is  the 
exchange  of  carbonic  acid  for  a  corresponding  amount  of 
oxygen  gas.  In  health,  during  quiet  breathing,  the  blood 
becomes  completely  saturated  with  oxygen. 

353.  Affinity  of   blood  for  oxygen.  —  Blood  exposed   to 

206  • 


RESPIRATION   OF  THE  TISSUES 


207 


the  air  takes  up  oxygen  very  readily  and  becomes  of  a 
bright  red  color.  Thus,  blood  as  it  usually  flows  from 
a  slight  wound,  takes  up 
oxygen  gas  almost  im- 
mediately and  becomes 
the  color  of  arterial  blood, 
and  venous  blood  is  sel- 
dom seen.  Between  the 
dark  color  of  the  venous 
blood  in  the  veins  of  the 
hands,  and  the  brighter 
pink  hue  of  the  surround- 
ing skin  due  to  the  capil- 

^      .  ,  .  Sketch  of  a  thin  slice  of  a  lung,  showing 

lanes,  tnere  is   a  contrast    the  arrangement  of    capillaries  upon  the 


which    is  a  good    indica- 


walls  of  the  air  sacs  (X  50) . 


tion    of     the    usual    differ-    ^   interior  of  an  air  sac. 

b   bottom  ofan  air  sac  covered  with  capillaries. 
ence  between  venous   and    c    side  of  an  air  sac  with  capillaries. 

arterial  blood. 

354.    Exchange  of  oxygen  and  carbonic  acid  in  the  lungs. 

—  The  blood  in  the  capil- 
laries of  the  lungs  is  sepa- 
rated from  the  air  in  the 
air  sacs  by  only  the  thin 
walls  of  the  capillaries. 
Oxygen  from  the  air  in 
the  air  cells  passes 
through  the  capillary 
walls  into  the  blood 
almost  as  readily  as 
though  there  were  no 
walls  at  all.  In  the  blood 
the  oxygen  combines  with 

the  hemoglobin  of  the  red  blood  cells,  and  the  blood  be- 


Capillaries  upon  the  sides  of  an  air  sac 

(X200). 


20S 


APPLIED   PHYSIOLOGY 


comes  of  a  brighter  red  color  as  it  gains  oxygen.  Car- 
bonic acid,  which  was  combined  with  the  alkalies  of  the 
blood  plasma,  passes  through  the  capillary  wall  into  the 
air  of  the  air  sac  as  easily  as  the  oxygen  entered  the  blood. 

355.  The  skin  and  stomach  as  respiratory  organs.  — - 
Wherever  the.  blood  tubes  are  in  contact  with  the  air, 
absorption  of  oxygen  will  take  place.  In  the  stomach  and 
intestine  the  blood  tubes  are  very  near  the  surface,  and 
are  in  contact  with  air  swallowed  with  the  food.  So  some 
oxygen  will  be  absorbed  and  some  carbonic  acid  gas  given 
off.  The  skin  also  absorbs  oxygen  and  gives  off  carbonic 
acid  gas.  In  a  frog  at  least  -^  of  the  respiration  is  per- 
formed in  this  way.  In  man,  about  2^0"  ^^  much  respira- 
tion is  carried  on  by  the  skin,  stomach,  and  intestine  as  by 
the  lungs. 

356.  Respiration  of  the  cells  of  the  body.  —  After  leaving 
the  lungs,  the  blood  is   distributed  through  the    arteries, 

and  enters  the  capillaries 
of  the  body.  As  it  enters 
the  capillaries  it  contains 
the  same  amount  of  gases 
as  when  it  left  the  lungs ; 
that  is,  each  100  cubic 
inches  of  blood  contains 
40  cubic  inches  of  car- 
bonic acid  gas  and  20  of 
oxygen.  As  it  leaves  the 
capillaries,  it  contains  the  same  amount  of  the  gases  as 
the  venous  blood  which  enters  the  lungs;  that  is,  each  100 
cubic  inches  contains  46  cubic  inches  of  carbonic  acid  gas 
and  12  of  oxygen.  The  exchange  in  the  capillaries  bal- 
ances the  exchange  in  the  lungs. 

When  a  piece  of  flesh  is  put  into  a  dish  of  blood,  oxygen 


Diagram  of  the  respiration  of  cells. 


RESPIRATION   OF  THE  TISSUES  209 

will  leave  the  red  blood  cells  and  combine  with  the  cells 
of  the  flesh.  In  a  similar  way  oxygen  leaves  the  red  blood 
cells  in  the  capillaries  and,  passing  through  their  thin  walls, 
unites  with  the  cells  of  the  body,  producing  carbonic  acid 
gas,  water,  and  urea.  The  water  and  urea  go  back  to  the 
blood  and  are  thrown  off  by  the  kidneys.  The  carbonic 
acid  gas  passes  through  the  capillary  wall  into  the  blood 
and  unites  with  the  alkalies  of  the  plasma.  This  goes  on  in 
every  capillary  and  cell  of  the  body  and  constitutes  the 
real  act  of  respiration.  The  lungs  and  red  blood  cells  are 
only  devices  for  carrying  oxygen  to  the  deep  cells  of  the 
body. 

357.  Oxidation  of  sugar  and  fat.  —  Neither  sugar  nor  fat 
becomes  a  living  part  of  the  cells  of  the  body,  but  after  being  absorbed 
both  are  oxidized  at  once  and  furnish  about  three  times  as  much  heat 
and  energy  as  the  albumin,  which  forms  a  part  of  the  cells.  But  oxi- 
dation in  the  body  is  a  hving  process,  and  requires  the  operation  of 
livinsf  tissues.  So  it  is  unlikely  that  it  occurs  in  the  blood  stream.  As 
sugar  is  absorbed,  the  cells  of  the  liver  take  it  into  their  own  substance, 
and  probably  oxidize  it  there.  In  the  same  way  the  fat  is  probably 
taken  up  by  the  epithelial  cells  of  the  air  sacs  of  the  lungs  and  oxidized. 
In  each  case  the  heat  is  distributed  through  the  whole  body  by  the 
blood. 

358.  Respiration  a  continuous  process.  —  When  the 
breath  is  held,  the  oxygen  in  the  lungs  and  that  carried 
by  the  red  blood  cells  is  sufficient  to  supply  the  body  for 
only  about  half  a  minute.  By  the  end  of  that  time  all  the 
blood  becomes  venous  and  a  great  shortness  of  breath  is 
felt. 

Oxygen  passes  from  the  lungs  through  the  blood  tubes 
to  the  cells  of  the  body  with  great  rapidity,  so  that  by  a 
few  deeper  breaths  enough  extra  oxygen  is  taken  up  by 
the  red  blood  cells  to  reheve  shortness  of  breath  caused 
by  their  lack  of  oxygen 

OV.  PHYSIOL. —  14 


2IO  APPLIED   PHYSIOLOGY 

359.  Amount  of  oxygen  used  daily.  — The  amount  of 
oxygen  used  in  the  body  is  constantly  varying.  During 
muscular  exertion  greater  power  is  required  than  when  the 
body  is  at  rest.  To  keep  up  the  increased  power,  more 
oxygen  must  leave  the  blood  and  unite  with  the  muscle 
cells.  During  sleep  less  oxygen  is  needed,  but  the  average 
amount  used  each  day  is  fairly  constant. 

It  is  a  simple  example  in  arithmetic  to  calculate  how  much  oxygen 
the  red  blood  cells  usually  carry. 

i8        =  no.  of  respirations  per  minute. 
30      =  no.  of  cubic  inches  of  air  in  each  inspiration. 
540      1=  no.  of  cubic  inches  of  air  inspired  each  minute. 

60 
32400  =  no.  of  cubic  inches  of  air  inspired  each  hour. 

.04  =  per  cent  of  air  which  enters  the  red  blood  cells  as  oxygen. 
1296    =  no.  of  cubic  inches  of  oxygen  entering  the  blood  each  hour. 
1296-=-  1720  =  0.75  =:  cubic  feet  of  oxygen  entering  the  blood  each  hour. 

0.75 

1.2    =  ounces  weight  of  a  cubic  foot  of  oxygen. 
0.9    =  ounces  of  oxygen  entering  the  blood  each  hour. 
24 


21.6    =  ounces  of  oxygen  entering  the  blood  each  day. 

Allowing  two  or  three  ounces  more  for  extra  exertions,  about  25 
ounces  of  oxygen  enter  the  body  each  day.  This  is  about  the  amount 
needed  to  oxidize  the  food  which  a  man  usually  eats. 

The  amount  of  carbonic  acid  given  out  is  about  the  same  as  the 
amount  of  oxygen  taken  in,  if  it  is  measured  in  cubic  inches.  But  since 
the  carbonic  acid  is  heavier,  it  amounts  to  about  30  ounces  a  day.  About 
20  ounces  of  water  are  also  breathed  out  each  day. 

360.  Effect  of  exercise  upon  the  amount  of  o:?:ygen 
absorbed.  —  In  quiet  breathing  each  red  blood  cell  is 
loaded  with  oxygen  to  its  full  capacity.  During  muscular 
exertion  the  heart  beats  more  forcibly  and  faster,  driving 
the  red  blood  cells  more  rapidly,  and  thus,  in  a  given  time, 
more  oxygen  will  be  carried.     But  when  the  cells  are  shot 


RESPIRATION   OF  THE  TISSUES  211 

through  the  capillaries  too  rapidly,  there  is  no  time  for 
either  giving  or  receiving  oxygen,  and  the  body  may  be 
actually  starved  of  oxygen.  So  the  average  amount  of 
oxygen  which  the  blood  can  carry  is  found  to  be  about 
25  ounces  daily. 

It  is  possible  to  educate  the  respiratory  muscles  so  that 
during  physical  exertion  they  act  more  regularly  and 
strongly.  As  a  result,  the  lungs  are  expanded  more,  and 
a  greater  area  of  capillaries  is  exposed  to  the  air.  The 
heart  also  may  be  trained  to  restrain  its  violent  action,  so 
that  the  blood  is  not  shot  through  the  capillaries  of  the 
lungs  too  rapidly  to  take  up  oxygen.  An  athlete  trains 
his  body  so  that  it  can  absorb  more  than  25  ounces  of 
oxygen  daily,  and  thus  he  can  put  forth  a  greater 
amount  of  exertion.  Such  a  person  is  said  to  be  lo7ig 
winded. 

361.  Causes  of  shortness  of  breath.  —  The  sensation  of  short- 
ness of  breath  is  usually  due  to  a  deficiency  of  oxygen  in  the  blood 
which  circulates  through  the  respiratory  center.  The  blood  contains 
too  little  oxygen  when  an  extra  amount  of  oxygen  is  used  during  great 
physical  exertion.  At  first,  the  heart  pumps  the  blood  faster  so  that  it 
carries  more  oxygen  in  a  given  time,  but  when  the  blood  is  pumped 
very  rapidly,  the  red  blood  cells  are  shot  through  the  lungs  so  quickly 
that  they  cannot  obtain  the  necessary  oxygen.  When,  as  in  heart  dis- 
ease, the  blood  is  pumped  too  slowly,  only  a  small  amount  of  oxygen  will 
be  carried  through  the  respiratory  center,  and  there  will  be  continuous 
difficulty  in  breathing.  Shortness  of  breath  is  often  the  first  sign  of 
heart  failure.  After  severe  hemorrhage  there  are  too  few  red  blood 
cells  to  carry  the  full  amount  of  oxygen,  and  so  shortness  of  breath  will 
be  felt.  Death  by  bleeding  is  due  to  suffocation  and  lack  of  oxygen. 
In  the  disease  called  anemia  there  are  too  few  red  blood  cells  to  carry 
oxygen,  and  so  there  is  shortness  of  breath  on  exertion.  When  the 
larynx  or  the  trachea  is  compressed  or  obstructed,  as  in  choking,  or 
when  the  smaller  bronchi  are  filled  with  mucus,  as  in  bronchitis,  oxygen 
is  prevented  from  entering  the  blood,  and  the  respiratory  center  feels  a 
great  shortness  of  breath. 


212  APPLIED    PHYSIOLOGY      ' 

362.  Oxygen  inhalations.  —  Since  the  red  blood  cells 
are  loaded  with  oxygen  to  their  full  capacity  as  they  leave 
the  lungs,  they  could  absorb  no  more  even  if  it  were  in- 
haled in  a  pure  form.  When  there  is  a  shortness  of  breath 
during  disease,  pure  oxygen  is  sometimes  inhaled  to  take 
the  place  of  the  diluted  oxygen  of  the  air.  When  the  lack 
of  oxygen  is  due  to  a  diminished  number  of  red  blood 
cells,  or  if  the  blood  flows  too  slowly  to  carry  enough  oxy- 
gen, inhaling  oxygen  can  do  no  good,  for  the  blood  cells 
leaving  the  lungs  are  already  loaded  with  it.  The  poisons 
of  certain  diseases  may  cause  the  arteries  to  contract  and 
the  heart  to  beat  with  great  force  and  rapidity.  Then  the 
blood  cells  may  move  so  quickly  that  they  have  no  time  to 
take  up  oxygen  from  the  lungs.  Neither  rest  nor  violent 
inspiratory  efforts  will  relieve  the  resulting  shortness  of 
breath,  but  more  oxygen  may  reach  the  blood  cells  if  it 
is  inhaled  in  a  pure  form. 

If  there  is  an  obstruction  to  the  entrance  of  air  into  the 
lungs,  more  oxygen  may  pass  the  obstruction  if  it  is  inhaled  in 
an  undiluted  form.  When  the  larynx  or  trachea  is  obstructed 
by  a  membrane  in  diphtheria,  or  when  the  small  bronchi  are 
filled  with  mucus,  as  in  bronchitis  and  pneumonia,  then  the 
inhalation  of  pure  oxygen  may  be  of  great  benefit. 

363.  Asphyxia.  — When  the  breath  is  held,  a  feeling  of 
discomfort  comes  on  in  about  half  a  minute,  which  soon 
becomes  great  distress.  If  a  person  is  prevented  from 
taking  a  breath,  he  will  become  unconscious  in  a  few 
seconds,  but  will  make  great  inspiratory  efforts  for  a 
minute  or  more.  There  will  be  convulsions,  and  the  face 
will  turn  purple,  for  all  the  blood  is  venous.  Death  will 
take  place  in  less  than  five  minutes.  This  is  called 
asphyxia.  At  any  time  before  death  actually  takes  place 
life  can  be  restored  by  artificial  respiration. 


RESPIRATION   OF  THE  TISSUES  213 

364.  Drowning.  —  Drowning  is  a  form  of  death  by 
asphyxia,  but  is  complicated  by  the  entrance  of  water  into 
the  lungs. 

The  treatment  of  drowning  is  simply  to  perform  artifi- 
cial respiration.  In  order  to  do  it,  it  will  be  necessary  to 
remove  the  water  from  the  lungs.  This  can  be  done  by 
turning  the  person  upon  his  face  and  forcibly  compressing 
his  back.  It  will  be  still  better  to  suspend  him  head  down- 
wards for  a  few  seconds,  or  standing  astride  him  to  raise 
him  up  and  down  about  twenty  times  a  minute  by  grasp- 
ing him  about  the  lower  part  of  the  chest.  This  performs 
artificial  respiration  and  lets  out  the  water  at  the  same  time. 

The  person's  limbs  should  be  rubbed  vigorously  toward 
the  heart  and  kept  warm  by  hot  water  bottles.  No  time 
should  be  lost  by  carrying  him  to  a  building,  but  artificial 
respiration  should  be  done  on  the  spot.  Even  if  the  per- 
son has  been  in  the  water  half  an  hour  or  more,  it  is 
possible  to  restore  life. 

365.  Electric  shock.  —  A  shock  of  electricity  kills  by 
overwhelming  the  nervous  mechanism  which  controls  the 
heart  and  lungs.  A  shocked  person  is  unconscious,  and 
apparently  lifeless,  and  yet  life  may  be  restored  by  artifi- 
cial respiration.  It  should  be  done  at  once,  and  continued 
for  a  long  time  if  life  is  not  quickly  restored. 

366.  Effect  of  alcohol  upon  the  lungs.  —  Alcohol  partially 
paralyzes  the  arteries  of  the  body  so  that  they  dilate  and 
permit  a  larger  quantity  of  blood  to  pass  through.  Thus, 
the  capillaries  of  the  lungs  may  be  distended  with  the  rest. 
Then  they  may  partly  fill  the  air  sacs  so  that  less  air  can 
enter.  If  the  distension  continues  for  some  time,  the  walls 
of  the  capillaries  may  thicken  so  that  oxygen  will  pass 
through  them  less  readily.  The  walls  of  the  air  sacs 
themselves  may  become  thickened,  and  the  exchange  of 


214  APPLIED   PHYSIOLOGY 

oxygen  and  carbonic  acid  impeded.     This  effect  may  be 
produced  by  continuous  moderate  drinking. 

367.  Alcohol  interferes  with  the  respiration  of  the  cells.  — 
Alcohol  is  quickly  absorbed  from  the  stomach  and  intes- 
tine and  as  quickly  disappears.  After  it  is  taken,  little 
or  no  alcohol,  or  any  substance  like  alcohol,  or  any  sub- 
stance containing  so  little  oxygen  as  alcohol,  can  be  found 
in  any  waste  of  the  body.  Hence  the  inference  is  that  it 
must  be  oxidized,  although  the  exact  point  and  the  manner 
of  its  oxidation  may  not  be  known.  But  the  evidence  for 
its  oxidation  is  the  same  as  that  for  the  oxidation  of  sugar. 

Every  ounce  of  alcohol  requires  nearly  two  ounces  of 
oxygen  to  oxidize  it  fully.  Taking  twenty-five  ounces  of 
oxygen  gas  as  the  amount  used  in  a  day,  there  will  be  only 
one  ounce  used  in  an  hour.  So  to  oxidize  an  ounce  of 
alcohol  takes  an  amount  of  oxygen  equal  to  the  whole 
supply  of  the  body  for  two  hours.  Three  or  four  drinks 
of  whisky  contain  this  ounce  of  alcohol.  If  this  amount 
is  drunk,  there  will  soon  be  a  lessened  action  and  a  nar- 
cotic effect  throughout  the  body,  due  mainly  to  the  lack 
of  oxygen.  A  noticeable  degree  of  uncertain  action  is 
called   hitoxication. 

Using  alcohol  in  the  body  is  like  burning  kerosene  in 
a  coal  stove.  By  taking  great  care  a  little  kerosene  can 
be  made  to  give  out  some  heat  from  the  stove,  but  the 
operation  is  dangerous.  Some  people  seem  to  oxidize 
alcohol  within  the  body  with  but  little  harm ;  but  they 
run  great  risks  of  doing  themselves  harm,  and  the  result 
is  not  nearly  so  good  as  if  they  had  used  proper  food. 

368.  Poisons  produced  by  alcohol.  —  When  too  little  oxy- 
gen enters  the  draft  of  the  stove,  the  wood  is  burned  imper- 
fectly, and  there  are  clouds  of  smoke  and  irritating  gases. 
So,  if  oxygen  goes  to  the  alcohol  and  too  little  reaches 


RESPIRATION   OF  THE  TISSUES  215 

the  cells,  instead  of  carbonic  acid  gas,  and  water,  and  urea 
being  formed,  there  are  other  products,  some  of  which  are 
exceedingly  poisonous  and  which  the  kidneys  handle  with 
difficulty.  The  poisons  retained  in  the  circulation  never 
fail  to  produce  their  poisonous  effects,  as  shown  by  head- 
aches, clouded  brain,  pain,  and  weakness  of  the  body. 
The  word  intoxication  means,  "in  a  state  of  poisoning." 
These  poisons  gradually  accumulate  as  the  alcohol  takes 
oxygen  from  the  cells.  The  worst  effects  come  last,  when 
the  brain  is  too  benumbed  to  judge  fairly  of  their  harm. 
It  is  not  true  that  alcohol  in  a  small  amount  is  beneficial. 
A  little  is  too  much,  if  it  takes  oxygen  which  would 
otherwise  be  available  to  oxidize  wholesome  food. 

369.  Effects  of  tobacco.  —  Tobacco  smoke  contains  the 
same  kind  of  poisons  as  the  tobacco,  with  other  irritating 
substances  added.  It  is  usually  sucked  into  the  mouth 
and  at  once  blown  out  again,  but  cigarette  smoke  is  com- 
monly drawn  into  the  lungs  and  afterwards  blown  out 
through  the  nose.  It  is  irritating  to  the  throat,  causing 
a  cough  and  rendering  it  more  liable  to  inflammation.  If 
inhaled  into  the  bronchi,  it  produces  still  greater  irritation, 
and  the  vaporized  nicotine  is  more  readily  absorbed  as  the 
smoke  is  inhaled  the  more  deeply.  Cigarettes  contain  the 
same  poisons  as  other  forms  of  tobacco,  and  often  contain 
other  poisons  which  are  added  to  flavor  them. 

370.  Respiration  in  birds.  —  The  lungs  of  all  land  ani- 
mals are  like  man's  lungs,  and  the  process  of  respiration 
is  the  same.  The  lungs  of  birds  are  fixed  in  the  upper 
part  of  the  thorax,  and  in  addition  they  are  provided  with 
two  smooth  bags,  each  somewhat  larger  than  the  lung. 
Each  bag  connects  with  the  air  sacs  of  the  lung,  and  also 
with  the  interior  of  the  larger  bones.  Respiration  can 
occur  in  the  bags  and  bones   as  well   as  in   the   lungs. 


2l6 


APPLIED   PHYSIOLOGY 


Gills  of  a  fish. 


The  air  bags  are  expanded  with  air  during  flight,  and 
thus  the  body  is  made  Hghter  in  proportion  to  its  size, 
in  order  that  the  bird  may  fly  more  easily. 

371.  Respiration  in  amphibious  animals.  —  Some  water 
animals,  like  the  porpoise  and  whale,  possess  lungs  like 

land  animals,  and  are  compelled 
to  come  to  the  surface  of  the 
water  in  order  to  breathe,  but 
fish  have  a  special  apparatus  so 
that  they  can  use  the  oxygen 
which  is  dissolved  in  water.  On 
each  side  of  a  fish's  head  is  a  slit- 
like opening  reaching  from  the  interior  of  the  mouth  to 
the  surface  of  the  body.  In  each  opening  are  four  half 
circles  of  limber  bone.  From  the  back  of  each  circle  a 
row  of  thin  fingerlike  plumes  projects,  so  that  it  looks 
like  a  red  feather  with  plumes  only  on  one  side.  These 
half  circles  are  the  gills.  Each  plume  contains  a  blood 
tube  which  is  separated  from  the  water  by  a  very  thin 
wall.  The  fish  forces  the  water  through  his  mouth  and 
out  between  the  gills,  and  the  oxygen  contained  in  it 
readily  passes  through  the  thin  wall  of  the  blood  vessel 
into  the  red  blood  cells. 

372.  Respiration  in  a  frog.  —  A  frog  in  the  tadpole 
form  is  provided  with  gills  which  project  into  the  water 
from  its  neck,  but  when  it  becomes  a  perfect  frog  the 
gills  disappear  and  lungs  are  formed.  But  the  frog's  skin 
is  able  to  absorb  oxygen  and  to  give  off  carbonic  acid 
gas  about  one  eighth  as  rapidly  as  the  lungs. 

373.  Respiration  in  insects.  —  In  insects  from  three  to 
nine  tubes  extend  into  each  side  of  the  abdomen  and 
divide  into  small  branches,  but  do  not  communicate  with 
any   cavity.      The   fluid  which   answers    for   the    insect's 


RESPIRATION   OF  THE  TISSUES  21/ 

blood  comes  in  contact  with  the  surface  of  the  tubes  and 
absorbs  oxygen  from  the  air  in  them.  As  they  possess  no 
hemoglobin  or  red  blood  cells,  oxygen  is  simply  dissolved 
in  the  blood ;  but  owing  to  the  small  size  of  their  bodies, 
this  is  sufficient  for  their  use. 

374.  Respiration  in  shellfish.  —  Shellfish,  such  as  oysters 
and  clams,  have  gills  like  fringes  along  their  front  edges. 
The  gills  are  covered  with  cilia  which  cause  currents  of 
water  bearing  food  and  air  to  flow  through  the  shell. 

375.  Respiration  in  plants.  —  A  plant  also  breathes. 
While  it  uses  heat  from  the  sun  in  the  manufacture  of 
starch  from  the  carbonic  acid  gas  and  water,  yet  for  its 
own  movements  it  requires  a  production  of  heat  within 
itself.  In  order  to  climb  a  pole  and  unfold  its  flowers,  a 
vine  requires  power  which  is  furnished  by  the  oxidation  of 
its  own  substance.  At  the  height  of  the  flowering  season 
the  temperature  of  the  plant  is  raised  slightly  above  that 
of  the  surrounding  atmosphere,  and  carbonic  acid  gas  is 
given  off.  In  every  case  the  heat  and  power  is  furnished 
by  oxidation  of  some  of  the  plant's  own  substance,  but  the 
amount  of  carbonic  acid  gas  given  off  is  insignificant  in 
comparison  with  the  amount  of  carbonic  acid  gas  which 
the  plant  uses  as  food.  A  little  oxygen  is  absorbed  by 
the  leaves,  but  it  is  small  in  amount  compared  with  what 
is  given  off  by  the  plant. 

SUMMARY 

1.  As  blood  passes  through  the  capillaries  of  the  lungs  it 

gives  carbonic  acid  gas  to  the  air  and  takes  about 
the  same  amount  of  oxygen  from  the  air. 

2.  As  blood  passes  through  the  capillaries  of  the  body  it 

gives  up  oxygen  to  the  cells  and  takes  carbonic  acid 
gas  from  the  cells. 


2l8  APPLIED    PHYSIOLOGY 

3.  The  exchange  in  the  two  sets  of  capillaries  balances. 

4.  Within   the    living  cells    the  oxygen  unites  with   the 

albumin,  fat,  and    sugar,  producing    carbonic  acid 
gas,  water,  and  urea. 

5.  About  twenty-five  ounces  of  oxygen  are  used  daily  in 

oxidizing  the  body. 

6.  When  not  enough  oxygen  is  present  within  the  body, 

there  is  a  shortness  of  breath. 

7.  Alcohol  often  causes  distension  and  thickening  of  the 

capillaries  and  of  the  walls  of  the  air  sacs,  so  that 
oxygen  passes  through  them  less  readily. 

8.  The  alcohol  of  three  or  four  strong  drinks  of  liquor 

uses  as  much  oxygen  as  would  supply  the  whole 
body  for  two  hours. 

9.  As  a  result  of  taking  oxygen  from  the  cells  of   the 

body,  the  cells  act  in  an  uncertain  manner,  which  is 
called  intoxication. 

10.  Tobacco  smoke  irritates  the  air  passages.     It  contains 

nicotine,  which  can  enter  and  poison  the  body. 

11.  All  kinds  of    animals  and    plants  breathe  in  oxygen 

and  give  off  carbonic  acid  gas. 

DEMONSTRATIONS 

89.  With  a  glass  tube,  blow  air  through  some  limewater,  and  notice 
that  it  grows  milky,  showing  the  presence  of  carbonic  acid  gas.  Breathe 
upon  a  cold  glass  and  notice  that  moisture  collects  from  the  breath. 
Call  attention  to  the  fact  that  bad  odors  in  the  breath  are  due  to  de- 
cayed teeth,  a  coated  tongue,  or  foul  stomach,  or  possibly  to  a  dirty  nose. 

90.  The  change  in  color  from  venous  to  arterial  blood  can  be  illus- 
trated by  cutting  into  a  thick  slice  of  beef.  At  first  the  cut  surface  is 
dark  and  purplish,  and  of  the  color  of  venous  blood.  But  in  a  few  sec- 
onds the  blood  in  the  meat  absorbs  oxygen  from  the  air  and  becomes 
bright  red  in  color  like  arterial  blood. 

91.  With  two  needles  tease  apart  a  bit  of  gill  from  a  shellfish  and 
examine  it  with  the  microscope  for  the  waving  cilia. 


RESPIRATION   OF  THE  TISSUES  219 

92.  Show  a  fish's  gills  and  if  possible  a  tadpole's  also.  "Wrig- 
glers," or  the  young  of  mosquitoes,  can  be  found  in  a  rain  barrel,  and 
are  very  interesting.  At  the  tail  there  is  a  tuft  of  stiff  hairs  through 
which  it  breathes.  They  wriggle  about  in  the  water  and  at  intervals 
come  to  the  surface  and  thrust  out  the  tuft  of  hairs  so  as  to  get  a  supply 
of  oxygen. 

REVIEW  TOPICS 

1.  Give  the  changes  occurring  in  the  air  within  the  lungs. 

2.  Give  the  changes  which  occur  in  the  blood  within  the 

lungs. 

3.  Show  that  the  blood  carries  oxygen. 

4.  Show  that  the  skin  and  stomach  are  respiratory  organs. 

5.  Show  that  the  cells  of  the  body  take  oxygen  and  give 

off  carbonic  acid  gas. 

6.  Show  that  the  blood  carries  carbonic  acid  gas. 

7.  Show    that    respiration    is    a   rapid    and    continuous 

process. 

8.  Calculate  how  much  oxygen  is  used  daily  and    how 

much  carbonic  acid  gas  is  given  off. 

9.  Show  why  a  person  becomes  lo7ig  winded  by  training. 

10.  Give  some  causes  of  shortness  of  breath. 

11.  Tell  when  and  why  inhalations  of  pure  oxygen  are  of 

benefit. 

12.  Give  the  effects  of  alcohol  upon  the  walls  of  the  air 

sacs. 

13.  Show  how  alcohol  affects  the  respiration  of  the  cells. 

14.  Show  how  alcohol  causes  poisons  to  develop  within  the 

body. 

15.  Give  the  effects  of  tobacco  upon  the  air  passages. 

16.  Show  how  respiration  is  modified  in  birds,  in  fish,  in 

frogs,  in  insects,  and  in  shellfish. 

17.  Explain  the  respiration  of  plants. 


CHAPTER   XXIV 

THE   AIR   AND   VENTILATION 

376.  Composition  of  air.  —  Every  lOO  parts  of  air  are 
composed  of  about  20  parts  of  oxygen  and  80  parts  of 
nitrogen :  yo "o  P^^  ^^^^  ^^  ^^^  ^^^  ^^  carbonic  acid  gas. 
Air  contains  water  in  varying  amount.  Some  dust  par- 
ticles are  always  floating  about,  and  also  a  few  living 
germs  of  plants  like  those  producing  mold  and  yeast. 
These  substances  are  found  in  all  air,  and  none  are 
harmful. 

377.  Ozone  in  the  air.  —  There  is  a  form  of  oxygen  called 
ozone  which  is  much  more  active  than  common  oxygen.  It 
can  be  made  by  passing  a  strong  current  of  electricity 
through  a  tube  of  oxygen.  During  thunderstorms  some  is 
formed,  which  imparts  a  peculiar  odor  and  exhilarating 
property  to  the  air.  Some  is  formed  in  pine  forests,  and 
to  it  the  beneficial  effects  of  the  forests  upon  consumptives 
may  be  due.  It  is  never  found  in  any  great  amount  in 
the  air. 

378.  Argon.  —  It  was  discovered  in  1894  that  the  part 
of  the  air  supposed  to  be  pure  nitrogen  contains  a  gas 
hitherto  unknown,  to  which  the  name  argon  has  been  given. 
One  per  cent  of  the  air  is  argon.  Like  nitrogen,  it  cannot 
be  made  to  unite  with  any  substance  directly  from  the  air, 
and  so  both  act  simply  to  dilute  the  oxygen.  But,  unlike 
nitrogen,  it  does  not  form  a  chemical  combination  with 
anything  at  all,  but  is  always  found  simply  mixed  with  the 

220 


THE  AIR  AND   VENTILATION  221 

air,  or  with  a  few  other  substances.     Its  discovery  has  not 
modified  our  ideas  of  the  physiological  effects  of  the  air. 

379.  Dust  in  the  lungs.  —  If  the  dust  in  the  air  is  small  in 
amount,  it  adheres  to  the  moist  surface  of  the  nose  and  pharynx,  and 
does  not  enter  the  trachea.  If  some  enters  the  trachea,  it  becomes 
entangled  in  the  cilia  of  the  epithelial  cells  and  is  forced  back  towards 
the  mouth  and  then  coughed  out.  If  the  air  is  very  dusty,  some  dust 
will  enter  the  air  sacs.  Instead  of  letting  it  remain  to  fill  up  the  lungs, 
nature  has  given  the  lymphatics  the  power  to  take  the  dust  particles 
and  to  carry  them  to  the  nearest  lymph  nodes,  where  they  are  deposited 
and  remain  harmless. 

380.  Occupation  diseases.  —  Even  though  the  lymph  nodes 
take  care  of  inhaled  dust,  after  a  while  the  continuous  irritation  of  the 
hard  particles  injures  the  delicate  lining  of  the  bronchi  and  air  sacs, 
and  causes  bronchitis  or  asthma  or  pneumonia.  Tool  grinders  are 
especially  liable  to  the  trouble,  for  the  fine  particles  of  stone  and  steel 
which  fly  off  in  their  work  and  are  inhaled,  cannot  be  taken  up  by  the 
lymphatics.  Potters,  miners,  flax  workers,  and  pearl  button  makers 
are  all  subject  to  lung  troubles  to  a  greater  degree  than  workers  in  a 
dustless  atmosphere.  Those  who  work  with  quicksilver  or  phosphorus 
are  liable  to  inhale  the  fumes  and  be  severely  poisoned. 

381.  Amount  of  oxygen  needed  to  support  life.  —  When 
inspired  air  contains  less  than  20  per  cent  of  oxygen,  a 
shortness  of  breath  comes  on,  which  is  in  proportion 
to  the  lack  of  oxygen.  A  candle  will  not  burn  in  air 
containing  less  than  17  per  cent  of  oxygen,  while  air 
containing  only  15  per  cent  of  oxygen  will  support  life, 
but  there  will  be  great  shortness  of  breath.  In  old  wells 
and  cellars  oxygen  is  often  replaced  by  carbonic  acid  gas, 
and  men  have  been  suffocated  in  them.  A  simple  test  of 
the  safety  of  entering  them  is  to  lower  a  lighted  candle 
into  the  suspected  place.  If  it  burns,  there  is  surely 
enough  oxygen  to  support  respiration.  When  the  amount 
of  oxygen  is  diminished  to  ten  per  cent,  animals  die  in  a 
few  moments  with  all  the  symptoms  of  suffocation. 


222  APPLIED    PHYSIOLOGY 

382.  Rarefied  air.  —  Every  square  inch  of  surface,  in- 
cluding that  of  the  body,  sustains  a  weight  of  fifteen 
pounds  of  air,  but  it  is  balanced  by  an  equal  pressure  of 
air  inside  the  body,  in  the  lungs  and  stomach  and  other 
cavities,  and  so  it  is  not  felt.  At  high  elevations  there  is  less 
atmosphere  pressing  from  above,  and  so  the  air  expands 
and  becomes  lighter.  Then  a  lung  full  of  air  will  contain 
less  oxygen.  At  a  height  of  three  and  a  half  miles  the  air 
is  only  one  half  as  dense  as  at  the  surface  of  the  earth, 
and  at  the  height  of  five  miles  it  is  almost  impossible  to 
breathe  enough  oxygen  to  sustain  life.  The  lessened 
pressure  upon  the  body  disturbs  the  flow  of  blood,  espe- 
cially in  the  brain,  and  produces  dizziness  and  fainting. 

In  mountainous  regions  the  air  is  lighter  and  holds  less 
moisture  than  in  lower  regions.  It  is  also  purer,  for  it  is 
removed  from  the  contamination  of  cities  which  crowd  the 
lower  waterways.  So  those  regions  are  favorable  for  those 
suffering  with  lung  diseases  such  as  consumption.  Proba- 
bly a  still  greater  benefit  is  derived  from  the  respiratory 
exercises  and  the  full  expansion  of  the  lungs  which  are 
necessary  in  order  to  obtain  sufficient  oxygen. 

383.  Effect  of  increased  pressure  of  air.  —  In  working 
under  water  in  laying  deep  foundations  for  buildings,  a 
large  box  called  a  caisson  is  sunk  to  the  bottom,  and  into  it 
air  is  forced  so  as  to  keep  out  the  water.  Men  work  within 
the  caisson  subjected  to  double  or  triple  the  natural  pres- 
sure of  air.  Although  more  air  is  inspired  with  each  breath, 
the  blood  does  not  seem  to  take  up  more  oxygen  than  usual ; 
but  the  increased  pressure  of  air  upon  the  arteries  and  veins 
produces  great  disturbances  of  the  circulation.  It  is  impos- 
sible to  remain  in  the  caisson  longer  than  an  hour  or  two 
at  a  time.  In  leaving  the  caisson,  the  air  pressure  must 
be  diminished  as  slowly  as  on  entering,  so  as  to  permit 


THE  AIR   AND   VENTILATION  223 

the  liberated  gases  to  expand  slowly.  The  ear  drums 
could  be  easily  ruptured  by  a  quick  change  in  pressure. 
Sometimes  the  pressure  causes  a  severe  injury  of  the 
spinal  cord. 

384.  Effects  of  carbonic  acid  gas.  —  Carbonic  acid  gas 
itself  has  very  little  harmful  effect  upon  the  body.  When 
air  containing  one  fourth  its  bulk  of  carbonic  acid  gas  is 
inhaled,  the  air  sacs  soon  contain  more  of  the  gas  than 
is  found  in  the  blood.  Then  carbonic  acid  gas  is  no  longer 
given  off,  but  remains  in  the  blood  and  air  sacs,  and  pre- 
vents the  entrance  of  oxygen.  Shortness  of  breath,  uncon- 
sciousness, and  death  soon  occur,  caused  mainly  by  the 
displacement  of  the  oxygen.  Carbonic  acid  has  been  used 
to  produce  insensibility  during  surgical  operations  but  its 
effects  cannot  be  controlled,  and  its  use  is  unsafe. 

When  many  persons  are  confined  in  a  small  room,  the 
oxygen  is  speedily  used  up,  and  carbonic  acid  gas  takes  its 
place.  When  the  amount  of  oxygen  is  diminished  to  ten 
per  cent,  death  will  occur,  caused  rather  by  the  lack  of 
oxygen  than  by  the  presence  of  the  carbonic  acid  gas  or 
other  substances  in  the  expired  air.  But  discomfort  will 
be  felt  long  before  the  oxygen  is  diminished  to  an  appre- 
ciable degree. 

385.  Foul  air.  —  Besides  the  carbonic  acid  gas,  the  ex- 
pired air  contains  a  greater  or  less  quantity  of  water  and 
of  foul-smelling  vapors.  Odors  are  constantly  given  off 
also  by  the  skin  of  the  most  cleanly  persons.  In  the  air 
of  a  closed  room  in  which  several  people  have  been  for 
some  time,  there  is  a  characteristic  odor  which  belongs  to 
man,  just  as  certain  odors  are  peculiar  to  different  lower 
animals.  These  odors  are  very  oppressive.  They  cause 
sickness  in  sensitive  persons  mainly  because  of  their 
unpleasantness.     This  effect  passes  off  when  pure  air  is 


224  APPLIED    PHYSIOLOGY 

breathed.  The  heat  of  a  closed  room  greatly  intensifies 
the  effect  of  the  foul  air. 

386.  Cause  of  bad  effects  of  foul  air.  —  No  one  thing  can 

be  found  in  stuffy  air  to  account  for  all  the  bad  feelings  which  it  pro- 
duces. The  diminution  of  oxygen  is  too  slight  to  produce  noticeable 
effects,  but  the  combination  of  heat  and  foul  odors  is  very  oppressive 
to  persons  not  accustomed  to  them,  while  the  carbonic  acid  gas  tends 
to  cause  drowsiness  and  dullness  of  mind.  Those  who  live  in  a  foul 
atmosphere  continually  are  usually  too  poor  to  buy  nourishing  food, 
and  too  busy  to  take  exercise  in  the  open  air,  and,  moreover,  are 
greatly  overworked.  These  causes  produce  even  more  ill  health  than 
the  foul  air. 

387.  Bad  odors.  —  Decaying  matter  gives  off  bad  odors.  Many 
animals  and  vegetables  have  an  offensive  smell,  and  in  many  manu- 
factures foul  odors  are  continually  poured  into  the  air.  These  odors 
in  the  air  are  seldom  harmful,  yet  the  source  of  the  odors  is  usually 
dangerous  to  health,  and  the  odors  are  given  off  as  a  warning.  It 
is  nearly  always  true,  that  harmful  things  have  an  offensive  smell  and 
taste.  So  a  bad  odor  reveals  a  decaying  body  which  might  poison  a 
well,  or  a  disease  which  might  be  communicated  to  others. 

Since  odors  are  only  signs,  the  danger  is  not  past  if  only  the  odor 
is  destroyed.  Ammonia,  carbolic  acid,  or  perfumery  may  mask  the 
odor,  but  they  only  obscure  the  source  of  danger. 

388.  Sewer  gas.  —  Sewer  gas  is  exceptionally  offensive 
and  penetrating.  The  odor  is  not  especially  harmful,  but 
disease  germs  which  are  emptied  into  the  sewer  from  sick 
rooms  are  easily  carried  with  the  gas.  Usually  the  strong 
odor  betrays  the  leak  in  the  pipes  before  the  germs  have 
gained  an  entrance. 

389.  Cellar  air.  —  Cellars  are  apt  to  be  closed,  so  that  little 
fresh  air  and  light  can  enter.  Decaying  vegetables  and  other  sub- 
stances may  accumulate  in  the  corners.  This  makes  a  breeding  place 
for  disease  germs,  which  may  be  carried  up  through  the  floors  into 
living  rooms  above.  A  cellar  should  be  kept  dry,  clean,  and  well 
aired. 


THE   AIR   AND   VENTILATION  225 

390.  Malaria.  —  Malaria,  chills  and  fever,  fever  and 
ague,  or  intermittent  fever,  as  the  disease  is  variously 
called,  is  caused  by  germs  which  come  from  stagnant 
water  or  wet  earth.  The  air  in  low  localities  within  a  few 
rods  of  a  marsh  may  be  full  of  the  germs,  while  a  hill  in 
its  midst  may  be  free. 

Drainage  of  infected  ponds,  or  sleeping  in  the  upper 
stories  of  houses,  or  removing  to  a  hill  overlooking  the 
marsh,  will  probably  overcome  the  infection.  Newly 
turned  earth  or  damp  cellars  may  also  be  breeding  places 
for  the  disease. 

391.  Night  air.  —  There  is  a  popular  belief  that  during  the  night 
the  air  contains  some  harmful  substance  which  disappears  during  the 
day.  But  the  air  of  the  early  evening,  which  is  supposed  to  be  the 
worst  air  of  the  day,  has  been  purified  by  hours  of  sunshine,  while 
the  air  of  early  morning,  which  is  supposed  to  be  the  best  of  the  day, 
has  been  exposed  to  hours  of  the  noxious  influences  of  darkness.  So 
the  belief  is  a  contradiction  in  itself. 

392.  Contamination  of  air  by  fire  and  light.  —  In  addi- 
tion to  the  impurities  produced  by  breathing,  the  air  of 
inhabited  rooms  is  further  rendered  impure  by  iires  and 
lamps.  A  tallow  candle  will  consume  half  as  much  oxy- 
gen in  a  given  time  as  a  man.  A  lamp  burning  a  pint  of 
oil  in  an  evening  uses  as  much  oxygen,  and  gives  off  as 
much  carbonic  acid,  as  a  man  gives  off  during  a  whole 
day.  A  stove  uses  an  immense  amount  of  oxygen,  but  the 
gases  pass  up  the  chimney.  Candles  and  lamps  often 
pour  bad-smelling  gases  into  the  air. 

393.  Coal  gas.  —  When  coal  is  heated,  it  gives  off  a  gas  called 
carbonic  oxide.  Carbonic  oxide  is  the  main  part  of  illuminating  gas, 
and  in  a  stove,  burns  with  a  blue  flame.  It  is  extremely  poisonous 
when  breathed.  It  unites  with  the  hemoglobin  of  the  red  blood  cells 
and  destroys  their  power  of  carrying  oxygen.      Gas  from  a  smoking 

OV.    PHYSIOL. —  15 


226  APPLIED   PHYSIOLOGY 

coal  stove  or  a  leaking  gas  pipe  may  smother  a  whole  family  while  they 
are  asleep. 

In  treating  a  case  of  poisoning  by  gas,  an  abundance  of  fresh  air 
should  be  admitted,  and  artificial  respiration  should  be  performed. 

394.  Germs  of  disease  in  foul  air.  —  Disease  germs  may- 
be breathed  into  the  air.  If  the  air  of  a  room  smells 
stuffy,  it  is  a  hint  that  the  germs  as  well  as  the  stuffy- 
odors  may  be  accumulating.  Lung  diseases  are  especially 
frequent  among  those  who  work  in  close  rooms.'  The 
germs  of  measles,  scarlet  fever,  and  all  other  "catching" 
diseases,  are  also  likely  to  accumulate  in  a  close  room. 
Sick  persons  often  breathe  out  the  germs  of  disease,  which 
may  reenter  the  body  and  continue  the  disease.  More- 
over, every  discomfort  retards  recovery,  so  in  sick  rooms 
and  hospitals  a  continuous  supply  of  fresh  air  is  especially 
necessary,  while  in  every  room  the  air  should  be  changed 
often  enough  to  prevent  the  stuffy  odor  from  developing. 

395.  Consumption.  —  Tuberculosis  of  the  lungs,  or  consumption, 
is  an  infectious  disease,  caused  by  the  growth  of  living  germs  within 
the  lungs.  A  person  suffering  with  consumption  is  continually  giving 
off  the  germs  in  the  secretions  from  his  air  passages.  His  hajidker- 
chief  contains  millions  of  them.  While  moist  they  remain  on  the 
handkerchief  or  clothes,  but  when  dry  they  may  float  through  the  air, 
and  when  inhaled  may  produce  the  disease.  A  consumptive  is  always 
a  menace  to  other  occupants  of  a  room,  especially  if  he  does  not  exercise 
great  care  with  the  secretions  from  his  nose  and  mouth. 

396.  Ventilation.  —  Continually  replacing  the  impure  air 
of  a  room  with  fresh  air  is  vejitilation.  Nowadays,  with 
air-tight  rooms  and  closed  stoves,  openings  need  to  be  pro- 
vided for  the  exchange  of  air.  When,  by  breathing,  the 
quantity  of  carbonic  acid  gas  in  the  air  is  increased  by  one 
half  its  natural  amount,  other  substances  have  also  en- 
tered the  air,  so  that  it  begins  to  be  stuffy.     When  the 


THE  AIR  AND   VENTILATION  22/ 

quantity  of  carbonic  acid  gas  is  doubled,  the  air  is  mark- 
edly oppressive.  If  the  carbonic  acid  gas  is  increased  to 
three  times  its  natural  amount,  the  air  is  too  oppressive  for 
comfort,  and  may  contain  enough  germs  of  disease  to  be 
dangerous  to  health. 

397.  Computation  of  amount  of  fresh  air.  —  About  ^^^  per 

cent  of  fresh  air  is  carbonic  acid  gas.  When  j^-^  per  cent  more  of 
carbonic  acid  gas  has  been  added  to  the  air,  the  air  begins  to  be  stuffy 
and  unfit  for  use.  Suppose  there  is  an  air-tight  room  twenty  feet  square, 
and  ten  feet  in  height,  and  in  it  one  man  is  living ;  the  room  will  con- 
tain 4000  cubic  feet,  jl^  per  cent  of  4000  cubic  feet  is  ^o  of  a  cubic 
foot,  which  is  nearly  the  average  amount  of  carbonic  acid  gas  breathed 
out  by  the  man  each  hour.  Thus  in  an  hour  a  man  renders  4000  cubic 
feet  of  fresh  air  stuffy.  In  reckoning  the  amount  of  fresh  air  to  be 
admitted  to  rooms,  4000  cubic  feet  per  hour  is  the  smallest  amount 
which  can  be  safely  allowed.  Therefore,  if  only  one  person  breathes 
the  air  of  a  room  twenty  feet  "square,  and  ten  feet  high,  the  air  needs 
to  be  wholly  renewed  each  hour,  and  yet  it  contains  enough  oxygen  to 
last  a  week.  Fresh  air  is  needed  when  the  air  of  a  room  smells  stuffy 
to  a  person  coming  from  pure  air. 

398.  Natural  ventilation.  —  When  air  is  heated  it  ex- 
pands so  as  to  fill  more  space.  While  a  cubic  foot  of  air 
at  a  temperature  of  32°  F.  weighs  about  1.2  ounces,  at 
80°  F.  it  weighs  about  i.i  ounces.  So  heated  air,  being 
lighter,  tends  to  rise.  The  air  is  shghtly  warmed  in 
breathing,  and  so  tends  to  rise  to  the  ceiling,  while  the 
cool  air  which  enters  the  room  remains  near  the  floor. 
So  the  floor  is  usually  cooler  than  the  ceiling.  If  an 
opening  is  made  near  the  ceiling,  and  another  near  the 
floor,  the  warm  air  of  the  breath  will  naturally  pass  out  at 
the  upper  opening,  and  the  cool  fresh  air  will  enter  the 
lower  opening.  If  only  a  few  persons  are  in  a  room, 
the  openings  about  windows  and  doors  may  be  sufficient 
without  special  ventilation.     If  many  persons  are  together 


228 


APPLIED    PHYSIOLOGY 


in  a  room,  the  natural  cracks  and  openings  are  not  suffi- 
cient, but  other  openings  must  be  made. 

399.  Methods  of  ventilation.  —  In  ventilation  a  per- 
ceptible current  of  air  must  be  avoided,  for  many  people 
easily  take  cold  when  a  single  part  of  the  body  is  cooled 


Diagram  of  the  natural  ventilation  of  a  room. 

The  arrows  indicate  the  direction  of  the  air  currents. 

as  by  a  draft.  The  air  of  a  room  can  be  changed  only 
three  times  an  hour  without  producing  noticeable  drafts 
throughout  the  room. 

Many  devices  have  been  used  to  secure  an  even  distribution  of  the 
incoming  fresh  air.  The  simplest  is  to  lower  the  upper  window  sash. 
Warm  air  will  pass  out  above  the  upper  sash,  while  the  cooler  fresh  air 
will  enter  between  the  two  sashes,  and  will  be  given  an  upward  direc- 


THE  AIR  AND   VENTILATION  229 

tion  toward  the  warmer  air  of  the  ceiling.  There  it  will  become  warm, 
and  finally  will  spread  through  the  room  like  a  gentle  shower,  instead 
of  in  a  rushing  stream. 

A  modification  of  the  same  idea  is  to  raise  the  lower  sash  a  few  inches 
and  insert  a  narrow  board  in  the  lower  opening,  so  that  a  space  is  left 
between  the  sashes  for  the  entrance  of  fresh  air.  The  opening  for  fresh 
air  may  be  through  the  floor  under  the  stove,  and  thus  the  air  will  be 
heated  as  it  enters  the  room.  An  open  fireplace  produces  an  upward 
current  of  air.  An  opening  into  the  chimney  flue  near  the  ceiling  will 
carry  off  much  of  the  foul  air. 

In  manv  churches  a  small  part  of  the  window  is  hinged  so  that  its 
top  can  incline  inward.  If  the  window  is  placed  about  two  thirds  of 
the  way  between  the  floor  and  ceiling,  the  warm  air  will  pass  out  above 
the  window,  while  the  cool,  fresh  air  will  enter  below  it.  The  inclina- 
tion of  the  wdndow  will  cause  the  air  to  flow  toward  the  ceiling  at  first, 
w^here  it  will  be  warmed  and  scattered  so  that  it  cannot  produce  drafts 
upon  the  heads  of  the  listeners.  The  addition  of  an  opening  in  the 
center  of  the  ceiling  for  the  escape  of  the  warm  air  forms  an  efficient 
mode  of  ventilation. 

Hot  air  registers  both  heat  and  ventilate  a  room,  if  care  is  taken  to 
admit  fresh  air  to  the  pipes.  The  hot  air  passes  up  from  the  furnace 
because  it  is  lighter.  An  opening  in  the  window  or  into  the  chimney 
is  needed  to  allow  the  air  of  the  room  to  escape,  so  that  the  warm  fresh 
air  can  enter. 

Since  on  a  cold  day  the  air  inside  a  room  is  much  warmer  than  the 
air  outside,  a  current  of  air  will  rush  through  every  crack,  so  that 
good  ventilation  will  be  secured  by  a  very  small  opening.  Since  on  a 
warm  summer's  day  the  air  inside  and  outside  is  nearly  of  the  same 
temperature,  large  openings  are  necessary  to  effect  the  change  of  air. 

400.  Forced  ventilation.  —  In  large  buildings,  such  as  factories 
and  theaters,  warm  fresh  air  is  forced  into  the  rooms  by  rotary  fans,  and 
the  impure  air  escapes  through  openings  in  the  ceiling.  Thus  the 
amount  of  heat  and  air  admitted  can  be  exactly  regulated. 

Another  way  of  ventilating  large  houses  is  to  suck  out  the  impure 
air  by  rotary  fans,  while  fresh  warm  air  is  ad  nitted  through  small  open- 
ings near  the  floor,  thus  preventing  drafts.  This  method  is  being 
adopted  in  large  buildings  to  the  exclusion  of  other  methods. 

401.  Filtration  of  air.  —  In  forced  ventilation  the  air  is  con- 
ducted through  a  large  box,  which   has  partitions  arranged  so  as  to 


230  APPLIED   PHYSIOLOGY 

break  the  air  current  and  allow  the  dust  to  settle.  In  some,  the  air  is 
passed  through  a  layer  of  cotton.  Cold  air  Contains  less  moisture  than 
warm  air,  and  unless  the  air  is  given  more  moisture  before  it  is  sent  to 
the  rooms,  it  will  be  very  dry.  So  a  pan  of  water  should  always  be 
kept  inside  the  air  box  of  a  furnace. 

402.  Schoolroom  ventilation.  —  Children  are  especially 
susceptible  to  unhealthful  surroundings,  and  the  air  of 
a  schoolroom,  in  which  they  spend  the  greater  part  of  the 
day,  should  be  kept  pure.  Pure  air  means  clearer  brains 
and  better  lessons,  and  may  determine  whether  or  not  a 
child  shall  gain  a  sufficient  knowledge  to  assure  his  suc- 
cess in  life.  In  every  half  day  of  school  it  is  well  to  allow 
a  short  recess  in  which  windows  and  doors  can  be  thrown 
wide  open  and  the  pupils  sent  out  to  get  deep  breaths  of 
oxygen  during  play. 

The  upper  sashes  of  all  the  windows  on  the  side  of  the 
schoolroom  away  from  the  wind  can  be  kept  open  a  space 
so  as  to  produce  a  gentle  outward  current  of  foul  air. 

If  the  upper  sashes  cannot  be  lowered,  the  lower  one 
can  be  raised  and  a  board  inserted  under  it  so  that  the 
only  opening  left  is  between  the  two  sashes. 

If  registers  or  special  means  of  ventilation  are  provided, 
they  should  be  watched  and  regulated  according  to  the 
needs  of  the  air. 

403.  Purification  of  the  atmosphere.  —  Although  it  is  con- 
tinually receiving  impurities,  the  atmosphere  as  a  whole  never  becomes 
foul,  for  the  process  of  purification  never  ceases.  First,  the  wind  scat- 
ters the  impurities  to  a  height  miles  above  our  heads  and  over  the  seas 
to  arctic  and  uninhabited  regions,  and  thus  dilutes  the  impurities. 
Second,  rain  washes  out  dust  and  germs  and  soot,  and  foul  gases,  and 
carries  them  into  the  earth.  Third,  sunlight  destroys  living  germs 
floating  in  the  air,  and  dries  up  stagnant  sources  of  impurities.  Fourth, 
plants,  both  on  land  and  in  the  sea,  absorb  carbonic  acid  gas  and 
restore  the  oxygen  to  the  air.  By  these  means  the  composition  of  the 
air  is  kept  always  the  same. 


THE  AIR  AND   VENTILATION  231 

SUMMARY 

1.  Air  is  essentially  oxygen  diluted  with  four  times  its 

volume  of  nitrogen. 

2.  When  the  amount  of  oxygen  is  diminished   there  is 

shortness  ot  breath. 

3.  Exhaled  carbonic  acid  gas  is  not  poisonous  in  itself, 

but  if  present  in  great  amounts  it  may  keep  oxygen 
out  of  the  lungs. 

4.  Foul-smelling  vapors,  carbonic  acid  gas,  moisture,  and 

the  contamination  by  fire  and  lights  make  the  air  of 
crowded  rooms  oppressive. 

5.  Coal  gas  inhaled  may  unite  with  the  hemoglobin  in  the 

red  blood  cells  so  that  they  will  not  carry  oxygen. 

6.  The  main  thing  to  be  feared  in  close  air  of  crowded 

rooms  is  the  disease  germs  which  may  be  breathed 
into  it. 

7.  The  air  of  a  room  should  be  changed  often  enough  to 

allow  4000  cubic  feet  of   fresh  air  to  each  person 
each  hour. 

8.  Breathed  air  is  warm,  and  tends  to  rise  and  pass  out  of 

cracks  and  openings  in  the  upper  part  of  the  rooms, 
while  cold,  fresh  air  enters  by  lower  openings. 

9.  In  large  buildings  the  foul   air   is   either  forced   or 

drawn  out   by  rotary  fans,  and  fresh  warmed   air 
enters  to  take  its  place. 
ro.    The  atmosphere  is  purified  by  winds,  rain,  sunlight, 
and  plants. 

DEMONSTRATIONS 

93.  The  harmlessness  of  carbonic  acid  gas  can  be  illustrated  by 
soda  water,  which  is  water  in  which  a  large  amount  of  the  gas  is  held 
under  pressure.  Open  a  bottle  and  inhale  the  liberated  gas.  Notice 
its  pungent  odor  and  taste. 


232  APPLIED    PHYSIOLOGY 

94.  Hold  a  candle  or  lighted  match  near  each  crack  of  the  room  and 
notice  that  usually  the  flame  is  blown  towards  the  inside  from  cracks 
near  the  floor,  while  it  is  blown  outward  in  cracks  higher  up. 

95.  Clap  two  blackboard  erasers  together  to  make  a  small  cloud  of 
dust,  and  watch  the  movements  of  the  particles  in  a  ray  of  sunlight,  so 
as  to  detect  the  direction  of  the  air  currents  in  the  room. 

96.  Show  methods  of  ventilation  by  lowering  the  upper  sash ;  by 
raising  the  lower  and  inserting  a  board  in  the  opening.  Show  and 
explain  the  methods  of  ventilation  adopted  in  the  school. 

REVIEW  TOPICS 

1.  Give  the  composition  of  the  air. 

2.  Describe  ozone  ;  argon  ;  nature's  method  of  removing 

dust  from  inspired  air ;  and  the  dangers  of  inhaling 
dust  in  certain  trades. 

3.  Tell  how  much  oxygen  is  needed  in  the  air  to  sustain 

life,  and  give  a  simple  test  to  determine  whether 
sufficient  is  present. 

4.  Give  the  effects  of  rarefied  air,  and  air  under  increased 

pressure. 

5.  Give  the  effects  of  carbonic  acid  gas. 

6.  Describe  foul  air  and  its  effects. 

7.  Discuss  the  meaning  and  the  effects  of  bad  odors ;  of 

sewer  gas ;  of  night  air ;  and  of  cellar  air. 

8.  Describe  malaria. 

9.  Show  how  fire  and  lights  contaminate  the  air. 

10.  Describe  coal  gas  poisoning. 

11.  Show  that  foul  air  may  contain  disease  germs. 

12.  Calculate  how  much  fresh  air  should  be  admitted  into 

a  given  room  for  a  given  number  of  persons. 

13.  Describe  how  ventilation  naturally  goes  on,  and  tell 

some  ways  of  assisting  nature  in  ventilation. 

14.  Tell  how  a  schoolroom  may  be  ventilated. 

15.  Tell  how  the  atmosphere  is  purified. 


CHAPTER   XXV 
HEAT  AND   CLOTHING 

404.  Temperature  of  the  body.  —  During  health  a  man's 
body  has  a  temperature  of  98^°  F.,  which  does  not  change 
either  upon  the  warmest  day  in  summer  or  the  coldest  day 
in  winter.  The  body  is  warmed  by  the  oxidation  of  its 
own  cells  and  of  digested  food. 

405.  Change  of  heat  to  energy.  —  The  power  which  the 
body  puts  forth  in  performing  work  is  derived  from  the 
heat  of  oxidation.  The  work  of  the  '  heart  requires  the 
use  of  y^g-  of  all  the  heat  produced  in  the  body ;  the  respi- 
ration requires  -^ ;  digestion  and  absorption  require  a 
smaller  amount.  An  ordinary  day's  work  requires  -^q  of 
the  total  amount  of  heat.  So  nearly  three  fourths  of  all 
the  heat  produced  is  used  simply  to  heat  the  body. 

406.  Uniformity  of  temperature.  —  In  some  parts  of  the  body 

oxidation  is  many  times  more  active  than  in  others.  Probably  most 
of  the  sugar  is  oxidized  in  the  liver,  and  most  of  the  fat  in  the  lungs. 
As  tast  as  heat  is  developed  it  is  carried  all  over  the  body  by  the  blood, 
so  that  there  is  scarcely  half  a  degree's  difference  between  the  tem- 
perature in  any  two  parts.  Only  the  surface  of  the  skin  is  cooler 
because  it  comes  in  contact  with  cooler  air. 

407.  Fever.  —  When  the  temperature  of  the  body  is 
raised  only  a  degree  there  is  a  feeling  of  warmth  and  dis- 
comfort, which  is  called  2,  fever.  The  discomfort  is  worse 
as  the  temperature  is  higher.  A  temperature  of  104  de- 
grees is  a  high  fever,  and  if  continued  may  cause  death. 

233 


234  APPLIED    PHYSIOLOGY 

408.  Sensation  of  heat  and  cold.  —  If  the  temperature  is 
lowered  only  a  degree,  there  is  a  feeling  of  coldness  called 
a  chill.  A  chill  is  a  recognized  sign  of  beginning  illness. 
The  ordinary  feeling  of  heat  or  cold  is  due-  to  the  state  of 
the  nerves  of  the  skin,  whose  special  duty  is  to  conduct 
sensations  of  temperature.  These  nerves  are  so  abundant 
in  the  skin  that  their  sensations  overpower  the  sensations 
of  the  rest  of  the  nerves  of  the  body.  If  the  skin  is  warm, 
the  whole  body  feels  warm;  while  if  the  skin  is  cold,  the 
whole  body  feels  cold. 

409.  Chills  during  a  fever.  —  It  often  happens  during  a  fever 
that  the  blood  goes  to  deeper  parts,  leaving  the  skin  pale  and  without 
its  usual  supply  of  heat,  and  so  the  whole  body  feels  cold,  and  the  per- 
son has  a  chill,  although  the  temperature  of  the  body  may  be  raised 
several  degrees. 

In  severe  sickness  the  heart  is  sometimes  too  weak  to  pump  the 
blood  to  the  skin,  and  so  it  feels  cold,  although  the  temperature  of  the 
inside  of  the  body  may  be  raised  several  degrees.  This  condition  is 
often  called  inward  iever.  On  the  other  hand,  the  body  may  be  cold^ 
and  yet  if  the  blood  is  brought  to  the  surface,  the  person  will  feel  warm. 

410.  Regulation  of  the  heat  produced.  —  The  amount  of 
heat  produced  in  the  same  body  varies  widely  at  different 
times,  and  some  persons  always  produce  many  times  as 
much  as  do  others.  So  in  order  to  keep  the  temperature 
constant,  heat  must  be  given  off  at  one  time  and  saved  at 
another.  Nature  regulates  the  temperature  of  the  body 
by  varying  both  the  amount  produced  and  the  amount 
given  off.  The  production  of  heat  depends  partly  upon 
the  amount  of  food.  In  summer  man  naturally  eats  less 
than  in  winter.  Inhabitants  of  arctic  regions  eat  large 
quantities  of  fat,  the  oxidation  of  which  produces  a  large 
amount  of  heat,  while  the  inhabitants  of  hot  climates 
naturally  avoid  fat. 


HEAT   AND    CLOTHING  235 

The  production  of  heat  also  depends  upon  the  amount 
of  oxygen  taken  into  the  body.  In  work,  deeper  inspira- 
tions are  taken,  and  more  oxygen  reaches  the  cells,  and 
thus  exercise  warms  the  body. 

411.  Regulation  of  the  heat  given  off.  —  Nature  also 
regulates  the  amount  of  heat  given  off.  The  body  loses 
some  heat  through  the  breath,  and  more  by  contact  with 
the  cool  air.  When  the  temperature  of  the  inside  of  the 
body  is  raised,  the  blood  tubes  of  the  skin  dilate,  so  that 
more  blood  comes  in  contact  with  the  air.  If  the  tempera- 
ture falls  slightly  below  the  natural  point,  the  blood  tubes 
of  the  skin  contract,  so  that  less  blood  comes  to  the  sur- 
face, and  more  heat  is  retained  until  the  temperature  rises 
to  the  natural  point  again.  A  change  of  temperature  too 
small  to  be  felt  will  produce  these  changes  in  the  blood 
tubes  of  the  skin. 

412.  Effects  of  tight  bands.  — When  the  circulation  is  hindered 
so  that  less  blood  enters  any  part  of  the  body,  its  temperature  falls.  A 
finger  whose  veins  are  compressed  by  a  tight  string  becomes  percepti- 
bly cooler  in  less  than  a  minute.  Garters  often  cause  cold  feet  in  the 
same  way.  Compression  of  the  waist  may  cause  the  whole  body  to  feel 
cold. 

413.  Effects  of  perspiration.  —  Sometimes  men  work  in 
air  which  is  hotter  than  their  bodies.  Then  instead  of 
giving,  they  receive  heat.  In  order  to  keep  them  cool 
under  these  circumstances,  nature  has  provided  a  self- 
acting  bath  by  means  of  the  sweat,  ox  perspiration.  When 
the  temperature  of  the  body  is  raised  from  any  cause,  the 
perspiration  is  poured  out  in  greater  quantity,  which  in- 
creases as  the  quantity  of  heat  increases. 

The  heat  of  the  body  is  used  in  changing  the  water  of  the  perspira- 
tion to  steam,  which  then  passes  off  from  the  body.     The  process  is 


236  APPLIED    PHYSIOLOGY 

like  the  boiling  of  water  in  a  teakettle,  where  the  heat  passes  off  in  the 
steam,  so  that  the  temperature  of  the  water  does  not  rise  beyond  the 
boiling  point.  Some  perspiration  is  given  off  even  if  the  body  is  cold, 
but  with  an  overproduction  of  heat  more  perspiration  is  often  pro- 
duced than  can  be  turned  into  vapor.  A  person  is  usually  said  to  per- 
spire onlv  when  it  is  produced  in  so  great  a  quantity  that  it  collects  in 
drops  upon  the  skin. 

414.  Moisture  in  the  air.  —  When  there  is  a  great  amount  of 
moisture  in  the  air  on  a  hot  summer's  day,  the  perspiration  does  not 
evaporate  from  the  skin,  and  so  heat  is  retained  within  the  body,  and 
the  air  seems  •'  heavy"  and  oppressive.  On  such  days  tlie  humidity  of 
the  air  is  said  to  be  great.  Dry  air  at  a  temperature  of  90  or  95  degrees 
seems  cooler  than  moist,  humid  air  at  a  temperature  of  80. 

415.  Sunstroke.  —  Men  and  animals,  while  working,  pro- 
duce a  large  amount  of  heat.  On  excessively  hot  and  humid 
days  the  extra  heat  may  not  pass  off  so  fast  as  it  is  formed, 
but  may  accumulate  until  the  temperature  rises  several 
degrees.  The  increased  heat  overwhelms  the  body,  and 
produces  a  sudden  attack  of  faintness  called  sunstroke. 
The  unconsciousness  lasts  for  a  long  time,  and  is  followed 
by  great  weakness,  and  sometimes  by  death.  When  a 
person  is  sunstruck  he  should  be  laid  in  a  cool  place,  with 
his  head  lowest.  Cold  water  should  be  dashed  upon  his 
head  and  chest.  His  limbs  should  be  rubbed  to  help  the 
circulation. 

416.  Damp  days  in  winter.  —  While  moisture  in  the  air  makes 
the  body  warmer  in  summer,  in  the  winter  it  makes  the  air  seem  colder. 
Dry  air  is  a  poor  conductor  of  heat,  but  a  little  moisture  makes  it  a 
much  better  conductor.  So  a  damp  wind  rapidly  extracts  the  heat 
from  the  body,  and  seems  to  penetrate  even  thick  clothing.  Moist  air 
at  a  temperature  of  20  degrees  seems  colder  than  dry  air  at  zero. 

417.  Heating  living  rooms.  —  In  addition  to  the  means 
provided  by  nature,  man  is  often  compelled  to  add  devices 
of  his  own  for  regulating  the  heat  of  his  body.     Man  lives 


HEAT  AND   CLOTHING  237 

with  the  greatest  comfort  while  the  temperature  of  the 
air  is  about  70  degrees,  which  is  but  Httle  more  than  half- 
way between  the  temperature  of  freezing  and  the  heat  of 
the  blood.  A  temperature  of  80  degrees  feels  too  warm, 
while  90  degrees  is  hot,  and  gS^,  or  the  temperature  of  the 
body,  is  oppressive. 

In  winter  a  temperature  of  70  degrees  in  a  living  room 
feels  neither  warm  nor  cold,  and  the  change  between  it 
and  the  outside  cold  air  is  less  noticeable  than  at  any  other 
temperature.  A  temperature  of  75  or  80  degrees  feels  too 
warm,  and  when  the  person  goes  out  of  doors  the  cold  air 
produces  a  sudden  contraction  of  the  arteries  and  a  chill, 
which  often  results  in  taking  cold.  A  sleeping  room  should 
be  at  a  lower  temperature  than  a  living  room. 

418.  Clothing.  —  Man  protects  his  body  against  the  loss 
of  heat  by  covering  it  with  clothes.  Some  kinds  of  sub- 
stances readily  permit  heat  to  pass  through  them,  and  are 
called  g-ood  heat  conductor's,  while  others  carry  heat  poorly 
and  are  called /^^r  conductors.  Lhien  is  a  good  conductor 
of  heat.  It  is  a  poor  protection  against  cold,  for  it  lets 
out  the  heat  of  the  body,  but  it  makes  good  summer  cloth- 
ing. When  the  linen  clothing  is  adjusted  to  one  tempera- 
ture, a  change  to  cooler  air  is  quickly  and  suddenly  felt. 
Thus  it  is  an  undesirable  clothing  material  in  changeable 
climates  or  in  cold  weather. 

Cotton,  while  being  a  poorer  conductor  of  heat  than 
linen,  is  yet  too  good  a  conductor  to  protect  the  body  in 
cold  or  changing  weather,  unless  a  great  deal  is  worn. 

Wool  is  a  poor  conductor  of  heat.  When  the  tempera- 
ture is  suddenly  lowered,  it  permits  the  heat  of  the  body 
to  pass  off  but  slowly,  and  thus  gives  the  skin  time  to  ad- 
just itself  to  the  change.  In  summer  it  retains  too  much 
heat,  and  does  not  make  so  good  summer  clothing  as  cot- 


238  APPLIED   PHYSIOLOGY 

ton  or  linen,  but  when  the  temperature  of  the  air  is  higher 
than  that  of  the  body,  it  prevents  the  heat  from  entering, 
and  thus  is  cooler  than  linen  or  cotton.  So  men  who  tend 
hot  furnaces  are  cooler  if  they  wear  thick  flannel  than  if 
they  wear  linen  or  cotton. 

Silk  is  also  a  poor  conductor  of  heat.  While  more  ex- 
pensive than  wool,  it  is  lighter  in  weight  and  feels  softer 
to  the  skin,  and  so  makes  the  best  kind  of  clothing. 

Fur  is  the  poorest  conductor  of  all,  and  is  the  best  pro- 
tector against  cold.  Nature  has  given  a  thick  coat  of  fur 
to  animals  thaf  live  in  cold  regions.  In  winter  their  fur 
is  long  and  thick,  but  it  drops  out  during  spring,  and  a 
new  fur  grows  during  the  summer,  becoming  thick  and 
long  again  by  the  following  winter. 

Air  itself  is  a  poor  conductor  of  heat,  and  when  a  considerable  quan- 
tity is  imprisoned  in  the  meshes  of  cloth,  the  garment  offers  a  greater 
resistance  to  the  passage  of  heat.  So  loosely  woven  cloth  is  much 
warmer  than  cloth  made  up  of  tightly  twisted  thread.  Fur  is  warm 
largely  because  of  the  amount  of  air  which  it  imprisons.  For  the  same 
reason  loose  clothing  is  warmer  than  tight-fitting  clothes. 

419.  Color  and  hea.t.  — When  exposed  to  the  sun,  black  objects 
take  up  twice  as  much  heat  as  white  objects.  This  difference  of  tem- 
perature is  noticeable  in  clothing.  Light-colored  or  white  clothing  is 
best  for  summer,  and  dark-colored  or  black  for  winter. 

420.  Distribution  of  clothing.  —  The  different  parts  of  the 
body  vary  in  their  ability  to  resist  cold.  The  face  and  hands  usually 
need  no  covering.  The  feet  need  less  than  the  body,  while  the  back, 
chest,  and  abdomen  need  the  most.  Nature  has  distributed  fur  upon 
the  animaPs  body  in  the  same  way,  leaving  the  head  and  feet  poorly 
covered.  The  sense  of  warmth  is  the  best  guide  as  to  the  amount  of 
ckjthing  to  be  worn  on  any  part.  A  person  should  wear  enough  to 
keep  each  part  of  the  body  comfortably  warm,  while  no  part,  especially 
one  which  is  usually  left  uncovered,  should  be  covered  so  as  to  be 
uncomfortably  warm. 

Dampness  produces  cold  by  the  evaporation  of  water.     If  all  the 


HEAT  AND   CLOTHING  239 

clothing  is  wet,  heat  is  taken  from  the  whole  body  equally,  and  there  is 
equal  contraction  of  the  arteries  with  no  congestion  or  inflammation. 
But  if  a  single  part  is  wet,  it  feels  cold,  while  the  rest  of  the  body  is 
warm ;  so  wet  feet  often  produce  inflammation  of  different  parts  of 
the  body. 

Cold  feet.  —  When  the  feet  perspire  a  great  deal,  the  stockings 
and  soles  of  the  shoes  become  saturated  with  moisture  and  make  the 
feet  feel  as  cold  as  if  they  were  wet.  Thicker  stockings  make  the 
feet  perspire  still  more,  and  so  do  not  add  to  their  warmth.  Tight 
shoes  allow  of  no  ventilation,  and  so  the  moisture  is  retained,  and  the 
feet  are  wet  and  cold. 

Drying  the  shoes  and  stockings  every  night  before  the  fire  will  pre- 
vent their  becoming  saturated  with  moisture.  A  new  inside  sole  cut 
out  of  thick  paper  put  m  the  shoe  each  morning  will  absorb  moisture 
and  help  keep  the  feet  warm.  Rubber  boots  and  shoes  do  not  permit 
the  moisture  of  insensible  perspiration  to  pass  ofl",  and  so  they  seem- 
ingly cause  the  feet  to  perspire. 

Bathing  the  feet  each  morning  in  cold  water  and  drying  them  by 
brisk  rubbing  improves  the  circulation,  so  that  they  will  be  more  likely 
to  stay  warm  all  day. 

421.  Paper  as  a  protection  against  cold.  —  Paper  is  a  poor 

conductor  of  heat.  A  newspaper  wrapped  around  the  body  under  the 
coat  is  as  good  as  an  overcoat  for  warmth.  A  few  newspapers  spread 
between  the  quilts  of  a  bed  will  make  up  for  a  lack  of  bed  clothing  upon 
a  cold  night.  One  need  not  suffer  from  insufficient  clothing,  day  or 
night,  if  a  few  newspapers  are  at  hand. 

422.  Sufficient  clothing.  —  The  amount  of  clothing  which 
one  needs  depends  largely  upon  a  person's  occupation  and 
previous  habits.  A  day  laborer  seldom  needs  an  overcoat, 
but  works  in  his  shirt  sleeves,  while  a  clerk  would  be 
chilled  were  he  to  step  outdoors  without  extra  wraps.  It 
is  a  mistake  to  think  that  by  exposure  to  the  cold  one 
can  always  become  hardened  to  it.  It  is  true  only  when  a 
person  takes  active  exercise  and  lives  out  of  doors  continu- 
ously. The  body  cannot  adapt  itself  to  the  sudden  changes 
from  hours  spent  in  a  warm  room  to  an  hour  or  two  in  the 
cold  air.    Enough  clothing  should  be  worn  so  that  the  body 


240  APPLIED    PHYSIOLOGY 

does  not  feel  chilled  on  entering  the  cold  air.  When  by- 
exercise  the  body  feels  warm,  the  overcoat  may  be  unbut- 
toned or  removed,  but  while  resting  it  should  be  put  on  at 
once.  Children  often  get  cold  by  suddenly  cooling  off 
while  warm,  fearing  ridicule  if  they  should  put  on  their 
coats  during  a  few  moments'  rest  from  play. 

423.  Airing  clothes  at  night.  —  At  night  it  is  usually  best  to 
remove  all  clothing  worn  during  the  day.  Woolens  have  the  power  of 
absorbing  a  great  deal  of  moisture  without  feeling  damp.  But  the 
moisture  and  the  waste  matters  from  the  skin  should  be  removed  each 
night  by  thoroughly  airing  the  underclothes.  If  it  is  not  done,  the 
woolen  may  become  so  saturated  with  moisture  that  it  affords  no  more 
protection  than  cotton,  and  so  may  render  a  person  liable  to  take  cold. 

424.  Beds.  —  Feather  beds  and  thick  quilts  enable  a 
person  to  get  warm  when  he  goes  to  bed  on  a  cold  night, 
but  after  he  falls  asleep  he  becomes  too  warm  and  per- 
spires too  freely.  Then  he  throws  off  the  coverings,  and 
soon  the  evaporation  of  the  perspiration  makes  him  cold. 
The  changes  from  one  extreme  to  the  other  often  produce 
colds.  Feather  beds  warm  the  side  of  the  body  which  is 
buried  in  them,  while  the  other  side  is  cold.  This  unequal 
distribution  of  heat  is  the  common  cause  of  catching  cold. 
As  a  rule  a  plain  mattress  is  more  comfortable  and  gives 
a  more  even  heat  than  a  feather  bed ;  but  in  beds,  as  in 
clothing,  a  person's  sensation  forms  the  best  guide  as  to 
the  kind  to  be  used, 

425.  Effect  of  lowering  the  temperature  of  the  body.  — 
In  extremely  cold  weather  heat  may  be  lost  from  the  body 
faster  than  it  can  be  produced,  and  thus  the  temperature 
falls.  Then  the  body  and  mind  cannot  act,  but  become 
numb  and  sluggish,  just  as  the  hands  become  numb  and 
powerless  when  cold.  If  the  temperature  continues  to  fall, 
the  respiration  becomes  less,  and  as  the  cells  cease  to  act 


HEAT  AND   CLOTHING  24 1 

an  agreeable  feeling  of  drowsiness  steals  over  the  mind, 
until  the  actions  of  life  cease.  After  the  drowsy  feelings 
begin,  life  can  be  restored  only  by  applying  heat  to  the 
body  and  performing  artificial  respiration  so  as  to  start  the 
process  of  oxidation  again. 

426.  Frost  bites.  When  a  part  becomes  very  cold  the 
cells  may  be  seriously  injured  long  before  they  are  frozen. 
A  toe  or  an  ear  which  has  been  on  the  verge  of  freezing 
will  begin  to  prick  and  tingle  when  warmed.  For  a  long 
time  afterward,  sensations  varying  from  an  itching  to  severe 
pricking  and  smarting  will  cause  great  annoyance.  In 
severe  forms,  short  of  actual  freezing,  the  part  swells  and 
becomes  red  and  inflamed,  while  the  sensations  are  ex- 
tremely annoying.  A  part  which  is  actually  frozen  is 
likely  to  die.  The  part  turns  black  soon  after  being 
thawed,  and  has  no  feeling.  After  a  fevv^  days  the  dead 
part  comes  off,  leaving  a  raw  sore.  Fingers,  toes,  and 
ears  are  very  liable  to  become  frozen,  but  the  eyelids  are 
almost  the  last  thing  to  freeze. 

427.  Frozen  limbs.  —  When  a  sokition  of  a  substance  in  water 
freezes,  the  first  ice  formed  is  composed  of  crystals  of  pure  water,  while 
that  frozen  last  contains  most  of  the  dissolved  substance  imprisoned  in 
the  meshes  of  the  crystals.  The  cells  of  the  body  are  made  of  water 
in  which  albumin  and  mineral  substances  are  dissolved.  When  freez- 
ing occurs,  the  first  ice  is  composed  of  needles  of  pure  water  which  has 
been  taken  from  the  cells.  If  the  freezing  takes  place  rapidly,  the 
water  produces  swift  currents  which  break  down  the  delicate  framework 
of  the  cells  and  cause  their  death.  If  freezing  occurs  very  slowly,  the 
water  may  leave  the  cells  so  slowly  that  no  damage  is  done  by  the  tiny 
flood.  If  thawing  occurs  just  as  slowly,  the  water  mav  reenter  the 
cells  so  that  they  may  be  preserved  alive.  When  a  hand  or  a  foot  is 
frozen,  it  should  be  rubbed  gently  either  with  snow  or  else  while  im- 
mersed in  ice  water,  and  the  raising  of  the  temperature  of  the  water 
should  be  done  very  slowly,  taking,  at  least,  two  or  three  hours  for  the 
thawing  process.     The  preservation  of  the  frozen  part  depends  upon 

OV.  PHYSIOL.  —  16 


242  APPLIED   PHYSIOLOGY 

its  very  slow  thawing.  Never  apply  warmth  of  any  kind  to  a  frozen 
part,  and  avoid  sitting  near  a  warm  stove  afterwards. 

428.  Effects  of  raising  the  temperature  of  the  body.  — 

When  a  living  body  is  exposed  to  a  higher  temperature 
than  is  natural,  the  respiration  and  circulation  are  much 
increased  by  the  extra  heat  and  there  is  much  mental 
excitement.  In  fevers  there  are  usually  excitement  and 
delirium.  A  continuous  temperature  of  105  degrees  is 
usually  fatal. 

It  is  possible  to  work  in  an  atmosphere  which  has  a  temperature 
of  150  degrees  or  more,  and  men  have  remained  in  hot  ovens  for  many 
'minutes  without  harm.  Their  perspiration  flows  very  freely,  and  its 
evaporation  carries  off  the  extra  heat,  so  that  the  temperature  of  the 
body  does  not  rise.  If  the  perspiration  should  cease,  the  temperature 
of  the  body  would  rise  at  once,  and  death  would  soon  take  place. 

429.  Burns.  —  A  temperature  of  no  degrees  feels  very  warm,  1 15 
degrees  is  hot,  while  120  degrees  is  all  that  a  person  can  commonly 
stand.  A  temperature  higher  than  this  injures  the  cells  so  that  a  blister 
will  be  raised  in  a  few  minutes.  A  temperature  of  170  degrees  coagu- 
lates albumin  at  once  and  so  destroys  the  life  of  cells  which  it  touches. 
A  temperature  of  212  degrees,  or  boiling  point,  at  once  produces  a  deep 
scald,  while  higher  temperatures  burn  the  skin  to  a  crisp. 

Cold  water  applied  at  once  to  a  burn  prevents  its  extension  and 
soothes  the  smarting,  but  it  should  be  applied  only  for  a  short  time 
lest  it  should  injure  the  cells.  Common  baking  soda  is  one  of  the 
most  soothing  applications.  A  mixture  of  linseed  oil  and  lime  water 
is  a  good  application  for  continuous  use.  After  a  deep  burn  has  healed, 
a  puckered  scar  will  be  left,  but  the  scar  will  be  less  noticeable  if  healing 
is  hastened  by  skin  grafting. 

430.  Burning  clothing.  —  When  the  clothing  on  a  person  takes 
fire,  a  great  danger  is  that  the  flames  may  be  inhaled.  It  will  take 
some  time  for  the  flames  to  penetrate  to  the  flesh,  but  they  may  quickly 
spread  upward.  So  a  person  should  always  lie  down  at  once.  Then 
let  him  roll  over  and  over  so  as  to  crush  out  the  fire.  Even  if  the  fire 
is  not  extinguished,  the  flames  cannot  reach  the  face,  while  the  clothes 
can  be  removed  as  well  lying  down  as  while  standing.     In  helping  a 


HEAT  AND  CLOTHING  243 

person  whose  clothes  are  burning,  at  once  throw  the  person  to  the  floor. 
Many  have  lost  their  lives  by  persisting  in  standing  up  while  attempt- 
ing to  remove  the  burning  clothes. 

If  it  is  necessary  to  enter  a  burning  building,  or  to  carry  a  person 
whose  clothes  are  burning,  the  best  protection  will  be  to  wrap  a  thick 
coat  or  blanket  around  the  body.  A  thick  coat  wrapped  around  burning 
clothes  or  thrown  over  the  body  after  a  person  lies  down  will  quickly 
smother  the  flames. 

431.  Alcohol  and  heat.  —  The  amount  of  heat  in  the 
body  depends  upon  the  balance  between  its  production 
and  its  loss.  The  rapid  destruction  of  alcohol,  in  all 
probability,  yields  heat  too  rapidly  to  be  utilized  by  the 
body.  The  most  constant  effect  of  taking  alcohol  is  to 
dilate  the  arteries  of  the  skin,  so  that  an  extra  amount  of 
heat  is  lost.  More  heat  is  always  lost  than  is  produced. 
Alcohol  lessens  the  power  of  the  body  to  endure  cold.  On 
a  cold  day  when  the  arteries  of  the  skin  are  contracted  so 
that  there  is  but  little  blood  to  warm  its  nerves,  alcohol 
may  send  the  blood  to  these  nerves  and  produce  an  agree- 
able sense  of  warmth,  but  in  reality  this  feeling  of  warmth 
is  due  only  to  the  heat  which  is  passing  off  from  the  inte- 
rior of  the  body. 

432.  Regulation  of  temperature  in  the  dog.  —  The  temper- 
ature of  many  animals  is  slightly  above  man's  temperature, 
but  is  regulated  in  the  same  way.  Some,  like  dogs,  sweat  but 
little,  but  the  animal  takes  short  and  rapid  breaths  through 
his  open  mouth,  thus  creating  a  strong  current  of  air  over  its 
moist  surface.    The  evaporation  of  the  saliva  cools  the  blood. 

433.  Hibernation  of  animals.  —  When  winter  comes  on, 
some  animals,  like  the  woodchuck,  retire  into  their  holes 
and  go  to  sleep.  Their  temperature  falls  to  50  degrees, 
or  even  lower,  while  respiration  occurs  only  three  or  four 
times  a  minute.  Only  enough  oxidation  of  their  own 
bodies    occurs   to    keep    life    from    completely  dying   out. 


244  APPLIED    PHYSIOLOGY 

When  warm  weather  comes  again,  their  respiration  and 
temperature  rise  to  the  natural  point,  and  the  animal  re- 
sumes its  former  condition,  but  is  thin  from  the  oxidation 
of  its  fat  and  albumin  during  his  long  sleep.  The  dormant 
state  during  the  winter  is  called  Jiibcrnation. 

434.  Cold-blooded  animals.  —  In  frogs  and  snakes,  oxi- 
dation is  not  sufficient  to  raise  their  temperatures  much 
above  that  of  the  surrounding  air.  So  they  feel  cold  to 
the  touch,  and  are  called  cold-blooded.  On  warm  days 
they  do  not  lose  heat  so  rapidly,  and  more  heat  is  retained 
within  their  bodies,  and  thus  they  become  more  active. 
When  cold  weather  comes  on,  they  cannot  produce  enough 
heat  to  enable  them  to  move,  but  they  lie  unconscious 
until  warm  weather  comes  again. 

Insects  cannot  produce  enough  heat  during  winter  to 
enable  them  to  fly  about,  so  they  remain  apparently  life- 
less until  the  warm  weather  comes  again. 

SUMMARY 

1.  The  heat  developed  by  oxidation  is  distributed  through 

the  body  by  the  blood  so  that  everywhere  it  has  a 
temperature  of  98.5  degrees. 

2.  The  sensations  of   heat    and   cold    are  caused  by  the 

blood  circulating   in  the  skin.       If   little  circulates, 

we    feel    cold ;    while    if  much    circulates,    we   feel 
warm. 

3.  An    increased    quantity   of  food,   oxygen,   or   exercise 

increases  the  amount  of  heat  produced  in  the  body. 

4.  Heat  is  given  off  by  contact  of  the  skin  with  the  cold 

air  and  by  means  of  the  perspiration. 

5.  A  temperature  of  about  70  degrees  in  a  room  is  the 

most  comfortable. 


HEAT   AXD   CLOTHING  245 

6.  Moisture  in  the  air  prevents  the  evaporation  of  per- 

spiration, and  increases  the  feeling  of  warmth. 

7.  Fur,  silk,  woolen,  cotton,  and  linen  protect  the  body 

from  cold  in  the  order  given. 

8.  Raising  the  temperature  of   the  body  causes  excite- 

ment and  delirium. 

9.  Alcohol  dilates  the  arteries  of  the  skin  and  permits 

an  increased  loss  of  heat,  in  spite  of  the  feeling  of 
warmth. 
10.    In  animals  while  hibernating,  and  in  all  cold-blooded 
animals,  oxidation  is  feeble,  the  temperature  is  low, 
and  their  movements  are  sluggish. 

DEMONSTRATIONS 

97.  To  sho^Y  that  more  blood  goes  to  a  part,  and  that  it  becomes 
warmer  while  acting,  let  a  boy  roll  up  his  sleeve  and  hang  his  arm  by 
his  side.  Notice  that  the  veins  slowly  fill,  because  the  flow  of  blood  is 
slowed  by  running  up  hill.  Now  have  him  open  and  shut  his  hand 
rapidly,  and  notice  that  at  once  the  veins  become  filled  full  of  blood. 
After  a  moment  the  hand  feels  warmer  than  the  other,  especially  if 
they  were  a  little  cold  at  first. 

98.  Take  some  ice  water,  some  water  at  the  temperature  of  the  air, 
and  some  hot  water.  Notice  that  the  water  at  the  medium  temperature 
feels  warm  when  the  hands  have  just  been  taken  from  the  ice  water, 
but  cold  when  they  have  just  been  in  the  hot  water. 

99.  Feel  of  a  piece  of  iron  and  of  a  stone  after  exposing  both  to  the 
cool  outside  air.  Notice  that  the  iron  feels  colder,  for  it  takes  heat 
from  the  hand  faster. 

100.  To  show  that  obstructing  the  flow  of  blood  makes  a  part 
cold,  tie  a  string  rather  tightly  around  the  finger.  In  a  moment  it 
becomes  filled  with  venous  blood,  and  feels  cold,  for  the  blood  is 
not  renewed. 

loi.  That  the  sensation  of  heat  and  cold  depends  partly  upon  the 
amount  of  blood  in  the  skin  can  be  shown  by  holding  a  piece  of  ice  in 
the  hands  for  several  minutes.  At  first,  the  hands  feel  cold,  for  the 
arteries  are  contracted.      In  a  little  while  the  blood  circulates  freely 


246  APPLIED   PHYSIOLOGY 

again,  and  there  is  a  feeling  of  warmth,  although  the  ice  still  continues 
to  cool  the  hand. 

102.  Take  some  cotton  and  some  woolen  cloth  of  equal  thickness. 
Wet  them  and  notice  how  much  more  quickly  the  cotton  will  dry  than 
the  wool.  Wrap  them  around  the  hand  and  notice  that  the  woolen 
feels  warmer,  because  evaporation  from  it  does  not  carry  heat  away 
from  it  so  fast  as  from  the  cotton.  Then  blow  upon  them  and  notice 
how  much  colder  the  cotton  feels. 

103.  Place  two  pieces  of  ice  of  equal  size  in  the  sun  and  cover  one 
with  a  black  cloth  and  the  other  with  a  white  piece  of  the  same  kind, 
and  notice  that  the  piece  under  the  black  cloth  melts  faster. 

104.  Needles  of  water  crystals  can  be. shown  by  setting  aside  a  cup 
of  water  out  of  doors  until  it  just  begins  to  freeze,  if  it  is  a  cold  day,  or, 
if  it  is  a  warm  day,  by  putting  a  large  piece  of  ice  in  the  sun  and  break- 
ing it  when  it  is  half  melted.     Each  needle  is  pure  water. 

105.  A  wasp  or  a  fly  will  illustrate  the  hibernation  of  animals.  In 
winter  a  few  wasps  can  usually  be  found  in  a  sunny  garret  window. 
When  the  air  is  quite  warm,  the  wasps  will  be  lively,  and  as  it  becomes 
colder  they  become  more  sluggish,  until  at  night  they  are  apparently 
lifeless. 

REVIEW  TOPICS 

1.  Give  the  temperature  of  the  body  and  tell  how  the 

heat  is  distributed. 

2.  State  what   causes   sensations   of    heat  and   cold,   and 

how  the  body  may  feel  warm  while  it  is  cold,  and 
cold  while  it  is  warm. 

3.  State  how  the  production  of  heat  is  regulated. 

4.  State  how  the  amount  of  blood  in  the  skin  regulates 

the  amount  of  heat  given  off. 

5.  State  how  the   perspiration  regulates  the  amount  of 

heat  given  off. 

6.  State  how  tight  bands  about  a  limb  cause  cold  feet  or 

hands. 

7.  Give  the  best  temperature  of  living  rooms  and  of  bed 

rooms. 


HEAT  AND   CLOTHING  247 

8.  Give  the  effect  which  moisture  in  the  air  has  upon  the 

heat  of  the  body  during  summer  and  during  winter. 

9.  Give  the  value  of  linen  as  a  protection  against  heat 

and  cold  ;  of  cotton  ;  of  wool ;  of  fur ;  and  of  air. 

10.  State  how  color  affects  temperature. 

11.  State  how  much  clothing  should  be  worn,  and  how  it 

should  be  distributed  over  the  body. 

12.  Discuss  feather  beds  and  thick  bed  coverings. 

13.  Give  the  effects  of   lowering  the  temperature  of  the 

whole  body;  of  frost  bites;  of  frozen   limbs;  and 
their  treatment. 

14.  Give  the  effects  of   raising   the   temperature  of   the 

body,  as  in  fever  and  in  sunstroke. 

15.  Give  the  effects  of  alcohol  upon  the  temperature  of 

the  body. 

16.  State  how  a  dog's  temperature  is  regulated. 

17.  Describe  the  hibernation  of  animals. 

18.  Describe  oxidation  in  cold-blooded   animals,  and   in 

insects. 


CHAPTER   XXVI 

EXCRETION   AND   SEWAGE 

435.  Getting  rid  of  oxidized  and  waste  substances  is 
excretioi.  All  oxidations  in  the  body  produce  carbonic 
acid  gas  and  water.  In  addition,  the  oxidation  of  albu- 
min produces  a  substance  called  urea,  which  contains 
the  nitrogen  of  the  albumin.  These  substances  together 
with  the  minerals  or  ashes  left  from  the  burned  cells 
must  continuously  be  excreted  by  the  lungs,  liver,  intes- 
tine, skin,  and  kidneys.  The  kidneys  excrete  the  most 
harmful  of  the  waste  substances. 

436.  Difference  between  a  secretion  and  an  excretion.  — 
In  a  general  way,  anything  separated  from  the  blood  by 
glands  is  a  secretion.  But  the  term  strictly  is  applied  only 
to  those  substances  which,  like  saliva  and  gastric  juice, 
are  of  use  to  the  body.  Substances  which,  like  carbonic 
acid  gas  and  urea,  are  only  waste  and  harmful  products, 
are  true  exci'etions. 

437.  Sweat  glands.  —  Numerous  coiled  tubes  lined  with 
epithelium  project  into  the  skin  over  nearly  its  whole  sur- 
face. Each  tube  is  a  sweat  gland,,  whose  epithelium  is 
continually  secreting  the  sweat,  ox  perspiration.  They  are 
very  numerous  on  the  forehead,  chest,  palms  of  the  hands, 
and  soles  of  the  feet.  Only  a  few  are  found  in  the  upper 
part  of  the  back. 

438.  The  perspiration.  —  The  perspiration  is  over  99  per 
cent  water.  It  contains  a  small  amount  of  urea  and  min- 
eral substances.     Ordinarily  it  evaporates  so  fast  that  its 

248 


EXCRETION  AND   SEWAGE 


249 


presence  is  not  noticed.  Nearly  a  quart  of  water  a  day 
thus  passes  off  from  the  surface  of  the  body  in  insensible 
perspiration.  In  hot  weather  and  during  exercise  so  much 
is  produced  that  it  accumulates  in  drops  upon  the  skin. 

439.  The  kidneys.  —  The  main  work  of  excretion  is 
performed  by  the  kidneys.  There  are  two  kidneys,  one  on 
each  side  of  the  backbone,  half 
covered  by  the  two  lower  ribs.  Each 
kidney  is  bean-shaped,  about  four 
inches  in  length,  by  two  in  breadth, 
and  one  in  thickness.  It  is  com- 
posed of  millions  of  fine  tubes  made 
up  of  epithelial  cells;  they  unite,  and 
finally  open  into  a  pocket  on  the  side 
of  the  kidney. 

440.  How  the  kidneys  excrete. — 
The  epithelial  cells  of  the  tubes  have 
the  power  to  draw  urea  and  mineral 
substances  from  the  blood.  They 
also  extract  a  large  amount  of  water 
in  order  to  wash  away  the  excreted  matter.  The  excre- 
tion runs  down  a  tube  called  the  iireter  to  the  bladder. 
About  a  quart  and  a  half  of  a  fluid  called  iLvine  is  thus 
excreted  daily. 

441.  Kidney  disease.  —  Kidney  disease  usually  takes  the  form 
of  an  aggravated  bilious  attack.  There  are  headaches,  loss  of  appetite, 
coated  tongue,  and  great  weakness.  Usually  the  urine  is  diminished, 
and  contains  some  albumin  derived  from  the  blood. 

Urea  itself  is  as  harmless  as  carbonic  acid  gas  and  is  as  easily 
excreted,  but  when  oxidation  is  incomplete,  substances  are  produced 
which  are  as  much  more  harmful  than  urea  as  a  smoking  lamp  is  more 
unpleasant  than  one  burning  perfectly.  When  more  food  is  eaten  than 
can  be  oxidized,  poisons  are  developed  from  the  imperfectly  oxidized 
albumin.     Some  are  leucomaines  or  substances  like  them.     The  kid- 


Kidney  cut  across. 


250  APPLIED   PHYSIOLOGY 

neys  try  to  excrete  the  poisons,  but  they  become  overworked,  producing 
what  is  called  BrighCs  disease.  Then  the  sweat  glands  excrete  more  waste 
matters,  and  in  the  emergency  often  do  enough  to  relieve  the  kidneys. 

442.  Relation  of  the  skin  and  kidneys.  —  The  skin  excretes 
but  little  urea  compared  with  the  kidneys,  yet  its  capacity  for  excreting 
water  is  unlimited.  When  much  water  is  excreted  by  the  sweat  glands, 
only  a  little  is  excreted  by  the  kidneys,  and  when  little  perspiration  is 
formed,  the  kidneys  excrete  more  water.  The  amount  of  urea  remains 
nearly  the  same  from  day  to  day,  and  so  the  urine  will  be  more  colored 
at  one  time  than  another. 

The  amount  of  perspiration  is  governed  principally  by  the  tempera- 
ture, and  remains  nearly  the  same  whether  much  or  little  water  is  taken. 
The  amount  of  urine  is  increased  by  the  water  swallowed.  A  large 
amount  of  water  tends  to  w^ash  away  the  urea  more  perfectly.  Often 
when  one  thinks  that  he  has  kidney  trouble,  an  increased  amount  of 
water  swallowed  will  pass  through  the  kidneys  and  bring  their  secre- 
tion to  a  natural  appearance. 

443.  Excretion  of  poisons  swallowed.  —  When  poisons  have 
been  swallowed,  those  which  pass  by  the  liver  are  seized  by  the  kid- 
neys and  excreted.  Carbolic  acid  and  turpentine  are  thus  excreted  by 
the  kidney.  In  passing  through  the  kidneys  these  drugs  may  irritate 
their  cells  and  set  up  inflammation.  Most  drugs,  whether  they  are 
vegetable  or  mineral,  pass  out  by  the  kidneys. 

444.  Excretion  by  the  liver.  —  The  liver  is  constantly 
destroying  all  kinds  of  poisons,  which  it  receives  not  only 
from  the  blood  of  the  intestine,  but  also  from  the  rest  of 
the  body.  Two  bile  substances,  glycocholic  and  taurocholic 
acids,  are  probably  formed  directly  from  albumin ;  and 
while  they  are  excretory  products,  yet  they  are  elements 
essential  to  digestion.  Another  substance,  bilirubm,  con- 
tains most  of  the  waste  coloring  matter  of  the  blood. 
When  the  liver  fails  to  excrete  these  substances,  as  in 
jaundice,  they  pass  out  by  the  kidneys  and  color  their 
secretion  yellow. 

445.  Excretion  by  the  intestine.  —  Although  the  intes- 
tine absorbs  food,  yet  it  also  pours  out  some  waste  matters. 


EXCRETION  AND   SEWAGE  251 

When  the  intestine  does  not  expel  its  contents,  symptoms 
like  liver  and  kidney  diseases  arise.  So  the  intestine 
excretes  some  waste  matter.  Under  certain  conditions 
even  the  stomach  may  become  an  excretory  organ,  and 
vomiting  may  be  a  life-saving  act,  just  as  it  often  is  when 
poisons  are  swallowed. 

446.  Intemperance  and  kidney  disease. — Alcohol,  by 
disturbing  oxidation  and  the  liver,  is  especially  liable  to 
cause  the  production  of  poisons  whose  excretion  severely 
taxes  the  kidneys.  It  alone  causes  over  one  half  of  kidney 
diseases.  Candies,  pie,  cake,  and  preserves  are  all  eaten 
simply  for  their  taste,  and  usually  after  a  sufficient  amount 
of  proper  food  has  been  taken.  So,  in  oxidizing  this 
increased  amount  of  food,  some  must  be  imperfectly  oxi- 
dized. Thus  poisons  are  developed  and  the  kidneys  are 
overworked. 

Intemperance  in  sugar  eating  is  extremely  common.  It 
produces  imperfect  oxidation  in  the  same  way  as  alcohol, 
only  its  effects  are  much  slower  and  less  noticeable. 

447.  Sewage.  —  The  excretions  of  man  and  animals, 
together  with  the  dirty  water  used  in  washing,  is  sewage. 
Sewage  is  composed  of  substances  which  are  of  no  use  to 
man,  but  on  the  contrary  are  often  very  poisonous. 

448.  Purification  of  sewage.  —  Nature  is  very  efficient  in 
changing  sewage  so  that  it  is  no  longer  harmful.  In  the  upper  layers 
of  the  soil  it  is  fully  oxidized  to  carbonic  acid  gas  and  water  and  min- 
eral substances.  The  soil  can  dispose  of  a  great  quantity  of  sewage  and 
prevent  it  from  polluting  the  surrounding  wells.* 

In  the  second  place,  plants  feed  upon  sewage.  They  aid  in  its  oxi- 
dation and  use  it  as  food.  Thus  plants  may  form  again  the  substances 
which  were  oxidized  in  man's  body  so  that  he  may  eat  the  very  prod- 
ucts which  he  once  excreted. 

In  the  third  place,  running  water  washes  away  sewage,  and  by  means 
of  the  oxygen  which  it  always  contains  it  fully  oxidizes  the  excretions. 


252 


APPLIED   PHYSIOLOGY 


449.  Danger  from  sewage.  —  Sewage  often  is  a  poison 
itself,  and  when  much  is  collected  it  often  develops  poisons 
by  its  decay.       The  foul  smell   of  sewage  is  due  to  gas 

called  sezver  gas.  While 
the  gas  itself  is  but  slightly 
harmful,  yet  it  is  a  sign 
of  decay  and  of  lurking 
sources  of  danger.  Sew- 
age is  dangerous,  mainly 
because  it  may  furnish 
food  in  which  germs  of 
disease  may  grow.  Ty- 
phoid fever  is  often  trans- 
mitted in  this  way.  These 
germs  may  become  dry 
wherever  the  sewage  dries, 
and  may  then  rise  as  dust 
with  the  sewer  gas. 

450.  Disposal  of  sewage. 
—  In  thinly  settled  country 
places  nature  is  able  to  dis- 
pose of  the  sewage  so  that 
it  is  destroyed  wherever  it 
is  placed.  But  in  order  to  be 
sure  to  avoid  pollution,  the 
simplest  contrivance  is  to 
conduct  the  sewage  away 
from  the  house  and  into  a 
hole,  from  which  it  slowly  filters  through  the  ground. 

In  more  thickly  settled  places  the  hole  in  the  ground 
is  often  made  water-tight,  forming  a  cesspool. 

451.  Sewers. — Towns  and  cities  provide  large  under- 
ground   tubes  or   tunnels,    called  seiuers,   into   which    the 


Diagram  of  the  plumbing  of  a  house. 

a  sink  or  washstand. 

b  trap,  which  remains  full  of  water  and  pre- 
vents the  entrance  of  sewer  gas. 

c  air  pipe  for  ventilation  and  to  prevent  the 
water  from  being  sucked  out  of  the 
trap. 

d  waste  pipe,  down  which  the  slops  pass 
into  the  sewer. 

e   pipe  from  the  gutter  on  the  roof. 

/  waste  pipe  passing  under  the  street. 

g  ventilation  pipe. 


EXCRETION   AND   SEWAGE  253 

sewage  runs  from  each  house.  The  sewage  is  either 
emptied  into  running  water  and  is  carried  away  by  the 
current,  or  else  it  is  transported  to  a  distance  from  the 
city  and  spread  over  the  soil  of  a  farm,  where  it  becomes 
plant  food.  The  produce  raised  upon  the  farms  aids  in 
paying  the  expense  of  removing  the  sewage. 

452.  Plumbing.  —  In  houses  pipes  are  arranged  to  carry 
off  the  sewage  as  fast  as  it  is  formed  in  the  sinks,  wash- 
bowls, and  closets.  Since  they  open  into  a  common 
sewer  of  the  town,  sewer  gas  can  readily  enter  the 
houses.  To  keep  it  out,  each  pipe  is  bent  into  a  loop 
which  remains  full  of  liquid  and  prevents  the  entrance 
of  gas. 

453.  Cleanliness.  —  No  matter  how  good  the  natural  or  artificial 
drainage  may  be,  if  decaying  matter  is  left  in  cellars  it  may  poison  the 
air.  Sinks  may  become  clogged  and  poison  the  air,  while  slops  and 
dirty  dishes  may  be  carriers  of  disease.  So  cleanliness  is  of  great  im- 
portance, aside  from  its  mere  looks. 

454.  Choice  of  a  house.  —  Damp  soils  are  likely  to  breed  dis- 
ease. In  some  the  subsoil  is  clay  or  sohd  rock  and  does  not  permit 
the  sewage  to  pass  off.  Land  formed  by  filling  in  marshes  is  apt  to  be 
damp  and  malarious,  besides  affording  no  natural  drainage. 

The  site  for  the  home  should  also  be  such  that  the  barnyard  and 
outhouses  can  be  put  so  they  will  drain  away  from  the  house  and  well. 
Attention  to  these  details  of  drainage  is  of  far  more  importance  than 
the  natural  beauty  of  a  site. 

SUMMARY 

1.  Excretions    are   waste   and    poisonous    substances   ex- 

pelled from  the  body.     The  principal  ones  are  car- 
bonic acid  gas,  water,  urea,  and  mineral  matters. 

2.  Sweat,  or  perspiration,  is  formed  in  tubes  in  the  skin. 

It  excretes  some  urea  and  mineral  matters. 

3.  The  kidneys  are  collections  of  minute  tubes  which  sepa- 

rate urea,  mineral  matter,  and  water  from  the  blood. 


254  APPLIED    PHYSIOLOGY 

4.  When,  in    Bright's  disease,  or  from    any  other  cause, 

the  kidneys  cease  acting,  death   by  poisoning  soon 
takes  place. 

5.  The   skin  can  aid  the    kidneys,  but  cannot  take  their 

place. 

6.  Alcohol   causes   poisons   to    develop   whose   excretion 

overworks  the  kidneys. 

7.  The  liver  and   intestine  each  excrete  a  great  amount 

of  waste  and  poisonous  substances. 

8.  The    excretions    from    man    remain     poisonous    until 

destroyed    by   the    soil,    by    plants,    or   by    running 
water. 

9.  In  thickly  settled  districts  it  is  necessary  to  carry  off 

the  excretions  by  means  of  a  sewer. 

DEMONSTRATIONS 

106.  Carefully  weigh  several  boys  early  on  a  warm  day.  Have 
them  run  about  and  take  violent  exercise,  eating  and  drinking  nothing, 
or  only  known  amounts.  In  a  few  hours  weigh  them  again.  A  loss  of 
half  a  pound  or  more  may  be  noted. 

107.  Insensible  perspiration  may  be  shown  by  touching  a  cold  glass 
to  the  skin,  when  moisture  will  at  once  condense  upon  the  glass. 

108.  Secure  a  specimen  of  kidney  mounted  for  the  microscope. 
With  a  power  of  about  200  diameters  show  the  class  how  capillaries 
form  a  bunch  in  a  pocket  at  the  beginning  of  each  tube,  and  then  pass 
out  to  surround  the  tubes,  and  finally  unite  to  form  the  veins.  Show 
them  the  large  size  of  the  cells  of  the  tube. 

109.  Cut  open  a  pig's  or  sheep's  kidney  lengthwise  and  notice  the 
pocket  in  its  side  and  the  radiating  lines  of  the  kidney  reaching  almost 
to  the  surface  and  marking  the  course  of  the  tubes. 

no.  A  pot  of  growing  flowers  will  illustrate  nature's  method  of  dis- 
posing of  sewage.  Although  manure  and  dirty  water  are  poured  upon 
the  earth,  yet  they  give  out  no  odor,  but  become  fresh  and  clean  and 
nourish  the  plant. 

III.    Show  the  pupils  the  traps  for  sewer  gas  under  the  sinks. 


EXCRETION   AND   SEWAGE  255 

REVIEW  TOPICS 

1.  Explain   the   difference  between   a  secretion  and  an 

excretion. 

2.  Name  the  principal  excretions  and  tell  how  they  leave 

the  body. 

3.  Describe    sweat   glands  and   the    perspiration    as   an 

excretion. 

4.  Describe  the  kidneys  and  their  excretion. 

5.  Discuss   how  imperfect  oxidation    may  overwork  the 

kidneys. 

6.  Show  how  the  skin  aids  the  action  of  the  kidneys  and 

how  the  one  acts  less  when  the  other  is  more  active. 

7.  Show  how  alcohol  produces  kidney  diseases  and  how 

sugar  acts  in  the  same  way. 

8.  Describe  three  ways    in   which   nature   destroys   the 

excretions  of  man. 

9.  Discuss  the  dangers  which  may  arise  from  sewage. 

10.  Tell  how  sewage  is  disposed  of  in  cities. 

11.  Describe  how  sewer  gas  is  prevented  from  entering 

houses  through  waste  pipes. 


CHAPTER   XXVII 


THE  SKIN  AND  BATHING 


455.    The  derma.  —  The  skin 
which  covers  the  entire  body. 


_e 


.--4 


^"^^sSr^— 


=;-s?--=^  6S;' 


-.'  "^  '<.. 


— / 


<S^-h 


Ti- 


The  skin  (X  lOo), 

a  dead  layer  of  epidermis. 

b  growing  layer  of  cpiflermis. 

c  layer   of    ceils    containing   the   coloring 

matter  of  the  skin. 

d  papilla. 

e  sweat  gland. 

/  small  blood  tube. 

g  fibers  of  the  derma. 

h  fat  cells  in  the  derma. 

256 


is  the  tough,  loose  sack 
It  is  designed  to  protect 
the  body  and  to  give 
off  perspiration  and 
heat.  (See  pp.  235,  248.) 
The  main  part  of  the 
skin  is  a  tough,  elastic 
network  of  fibers,  called 
the  derma  or  cutis,  which 
forms  a  layer  from  -^^  to 
\  of  an  inch  in  thickness. 
The  derma  of  animals, 
when  tanned,  forms 
leather.  The  skin  is 
connected  with  the  body 
by  a  loose  network  of 
fibers  called  the  subcu- 
taneous tissue,  which  per- 
mits the  skin  to  move 
freely  over  the  deeper 
parts.  Over  some  parts 
of  the  body,  as  upon  the 
abdomen,  the  subcutane- 
ous tissue  contains  a 
thick  layer  of  fat. 


THE   SKIN  AND   BATHING 


257 


456.  The  epidermis.  —  The  derma  is  covered  with  a  layer 
of  epithelial  cells,  called  the  epidermis  or  cuticle.  New 
cells  are  continually  being  produced  in  the  deeper  layers 
of  the  epidermis,  while  the  older  cells  become  matted  in  a 
firm  mass  which  is  continually  being  worn  away.  These 
cells  are  directly  continuous  with  the  epithelial  cells  of  the 
mucous  membrane  and  are  of  the  same  nature.  The  epi- 
dermis has  no  nerves  and  no  blood  tubes.  '' 


A  com. 

457.  Upon  the  palms  of  the  hands  and  soles  of  the  feet  the  epi- 
dermis forms  a  very  thick  layer  for  the  better  protection  of  these  much- 
used  parts.  When  hard  labor  is  performed  with  the  hands,  nature 
causes  the  protecting  epidermis  in  the  exposed  parts  to  form  a  thick 
and  horny  spot  called  a  callus.  Sometimes  pressure  and  rubbing  cause 
a  small  area  to  become  thickened  so  that  a  point  of  hardened  cells  is 
formed  which  presses  into  the  deeper  parts  of  the  skin.     This  is  a  corn. 

When  the  skin  is  vigorously  rubbed,  or  certain  drugs  are  applied, 
the  deeper  layers  of  the  epidermis  are  killed,  and  water  accumulating 
between  them  and  the  outer  layers  raises  a  blister. 

458.  Color  of  the  skin.  —  The  deeper  layers  of  the  epidermis 
contain  colored  granules  which  give  the  peculiar  color  to  different  races 
of  men.  Exposure  to  the  sun's  rays  produces  a  darker  coloring  matter. 
In  some  people  the  coloring  matter  is  deposited  in  small  spots  called 

freckles. 

ov.  PHYSIOL.  — 17 


258 


APPLIED    PHYSIOLOGY 


459.  Skin  grafting.  —  A  spot  of  skin  deprived  of  epithe- 
lium is  tender  and  sore.  New  flesh  forms  over  its  surface, 
while  the  epithelial  cells  at  its  edge  produce  new  ones 
which  spread  over  the  whole  surface  and  complete  the 
healing.     If  they  do  not  grow,  the  new  flesh  sprouts  above 

the   skin,  forming 

§0!l    ^  .^^.^-^  //v?/^  flesh. 

%^-\^^''^^'^^^^  "  ■^^■"^^'•'■1^^-^         The  deeper  cells 

of    the    epidermis 

may  remain  alive 

for     some     hours 

after  being  cut  off 

from    the    body. 

^    ^  When  placed  upon 

a  clean  ulcer,  they 

^may    grow    and 

r  produce  a  new  epi- 

g  thelium.      This   is 

skin  grafting. 

460.  Papillae. 
—  From  the  sur- 
face of  the  derma 
small     projections 

about  200"  ^^  ^^ 
inch  in  length, 
called  papillce,  ex- 
tend a  short  dis- 
tance into  the  epidermis.  They  contain  nerves  of  feeling. 
The  papillae  over  a  small  area  sometimes  become  over- 
grown, so  that  they  project  above  the  skin,  forming  a 
wart.  Rows  of  papillae  form  the  fine  curved  lines  upon 
the  balls  of  the  fingers  and  the  palms  of  the  hands.  They 
are  most  numerous  where  the  sensation  of  touch  is  greatest. 


A  hair  (x  200). 

a  epidermis  of  the  skin. 

b  hair  shaft. 

c  sebaceous  gland. 

d  muscle  which  makes  the  hair  erect. 

e  epidermis  of  the  hair  root. 

/  fat  cells  in  the  derma. 

g  papilla  from  which  the  hair  grows. 


THE   SKIN  AND   BATHING 


259 


.  a 
.3 


461.  Hair.  —  Extending  obliquely  nearly  through  the 
derma  are  numerous  minute  tubes  lined  with  epithelium. 
Their  cells  become  joined  together  in  a  tough  string,  called 
a  hair,  which  projects  out  of  the  tube.  When  the  hair  is 
pulled  out,  the  epithelium  covering  the  projection  in  the 
tube  soon  produces  another  hair.  A  small  muscle  is 
attached  to  the  bottom  of  each  hair  root.  Cold  causes 
the  muscles  to  contract  and  to  pull  the  hair  tubes  to  an 
upright  position  imparting  to  the  skin  a  roughness  called 
goose  flesh.     Hair  covers  almost  the  entire  body. 

462.  Sebaceous  glands.  —  Near  each  hair  is  a  gland  called 
a  sebaceous  gland.  It  secretes  a  kind  of  oil,  which  softens 
the  skin  and  keeps  the  hair  glossy.  The  glands  are  espe- 
cially numerous  down  the  center  of  the  face.  When  their 
mouths  are  stopped  by 
dirt  they  often  become 
distended  and  form  small, 
black  spots  called  black- 
heads, which  are  often 
mistaken  for  small  worms. 

463.  Nails. —The  epi- 
dermis upon  the  backs  of 
the  last  joint  of  each  finger 
and  toe  is  hardened  into  a 
nail.  The  nail  is  formed 
at  its  back  part  and  is 
pushed  onward  in  its 
growth.  An  epithelial  cell 
remains  a  part  of  the  nail 
about  three  months  before  it  is  pushed  from  its  root  to  its 
end. 

464.  The  complexion.  —  In  health  the  skin  has  a  velvety  appear- 
ance, and  a  rosy  color,  and  is  free  from  spots  or  scales.     Its  moisture  is 


A  nail  (x  200). 

a  surface  of  the  nail. 

b   body  of  the  nail. 

c    epithelial  cells  just  before  they  are  welded 

into  a  nail. 
d  papillae. 
e    growing  epithelium. 


26o  APPLIED    PHYSIOLOGY 

of  the  proper  degree  to  cause  it  to  feel  soft  and  pliable.  Its  appearance 
is  changed  by  ill  health.  If  the  stomach  and  intestine  are  not  in  good 
order,  it  is  almost  impossible  for  the  skin  to  be  beautiful.  Plain  food, 
fresh  air,  and  exercise  make  a  beautiful  skin,  and  no  skin  can  be  beauti- 
ful without  them.  Cold  dry  air  or  exposure  to  the  sun's  rays  often 
cause  it  to  become  red  or  to  blister.  These  effects  are  much  greater 
upon  those  who  are  unaccustomed  to  the  exposure. 

465.  Care  of  the  complexion. — Washing  the  skin  with  soft 
water  and  soap  as  often  as  it  becomes  dirty,  and  following  it  by  a 
thorough  drying  with  a  soft  towel,  are  the  only  effective  means  of 
beautifying  the  skin.  Paint,  powder,  and  perfumery  cannot  cause  the 
skin  to  grow  more  beautiful.  They  simply  coat  its  outside,  and  at  the 
same  time  stop  its  sebaceous  and  sweat  glands,  so  that  when,  it  is 
removed  the  skin  looks  worse  than  before.  They  act  like  any  other 
dirt.  Many  of  these  preparations  contain  poisonous  minerals  such  as 
lead. 

Drugs  taken  internally  to  beautify  the  skin  act  mainly  through  the 
arsenic  which  they  contain.  Arsenic  destroys  the  blood  cells,  and  so 
gives  a  peculiar  paleness  to  the  skin.  Paleness  is  only  a  sign  of  poison- 
ing which  is  working  harm  to  the  health. 

466.  Absorbent  power  of  the  skin.  —  Since  the  outer  part 
of  the  epidermis  is  dry  and  dead  and  contains  no  blood 
tubes  or  lymphatics,  substances  rubbed  upon  the  skin 
will  not  be  absorbed.  So  man  can  handle  virulent  poisons 
and  disease  germs  without  danger.  On  the  other  hand, 
when  the  epithelium  is  removed,  the  exposed  blood  tubes 
and  lymphatics  take  up  drugs  and  poisons  very  readily. 
Drugs  may  be  absorbed  from  surgical  dressings,  and  germs 
of  disease  may  enter  through  even  a  minute  scratch. 

467.  Care  of  the  hair.  —  The  hair  of  man,  like  that  of  animals, 
is  soft  and  glossy  in  health,  but  often  dry  and  rough  during  disease. 
Daily  brushing  to  remove  the  dirt,  and  to  distribute  the  oily  secretion 
of  the  .sebaceous  glands,  will  keep  the  hair  in  the  best  condition.  All 
that  is  necessary  beyond  this  is  frequent  washing  with  soft  water.  The 
secretion  of  the  sebaceous  glands  is  sufficient  to  oil  the  hair  and  scalp. 
There  is  no  substance  which  will  cause  hair  to  grow,  neither  will  any 


THE   SKIN  AND   BATHING  261 

stop  its  growth.  When  hair  is  shaved  off,  it  soon  regains  its  former 
length  and  then  ceases  to  grow.  Shaving  seems  to  have  some  effect 
in  causing  the  hair  to  grow  coarser,  but  it  does  not  add  to  the  number 
of  separate  hairs. 

468.  The  beard.  —  At  about  the  age  of  sixteen  the  hair  upon  a 
boy's  face  begins  to  grow  larger  and  coarser,  and  if  let  alone  becomes 
a  full  beard  in  the  course  of  two  or  three  years.  A  shaved  beard  is  not 
so  silky  as  one  that  has  never  been  cut. 

A  beard  gives  to  a  young  man  an  appearance  of  age  and  experience 
and  is  popularly  taken  for  a  sign  of  mental  and  physical  strength.  As 
a  matter  of  fact  the  presence  or  absence  of  a  beard  has  nothing  to  do 
with  a  person's  experience  or  knowledge. 

469.  Care  of  the  nails.  —  Biting  the  nails  makes  their  edges 
ragged,  besides  making  the  ends  of  the  fingers  sore.  The  nails  them- 
selves are  not  poisonous,  but  underneath  their  projecting  ends  germs 
of  disease  may  be  mixed  with  the  dirt  which  gathers  there.  Naturally 
the  nail  adheres  to  the  finger  nearly  down  to  its  end,  but  is  often  kept 
raised  and  sore  by  too  persistent  cleaning.  The  edge  of  the  semicircle 
of  flesh  surrounding  the  root  of  the  nail  is  naturally  soft  and  slightly 
raised  so  that  it  looks  like  a  fine  silken  braid.  Sometimes  it  becomes 
hard  and  cracks,  especially  upon  cold,  dry  days.  Cutting  away  the 
hard  edge  down  to  its  soft  margin  in  the  flesh  prevents  the  extension 
of  the  cracks.  A  tiny  sliver  of  the  edge  of  flesh  around  the  nail  torn 
back  into  the  flesh  forms  a  Jiangnail.  The  hangnail  should  be  cut  oflf 
close  to  the  flesh.  It  is  best  prevented  by  gently  pushing  the  skin 
back  from  the  nail.  Tight  shoes  bind  the  toes  together,  curving  the 
great  toe  nail  into  the  flesh,  causing  an  ingrowing  toe  nail.  Broad 
shoes  are  the  best  preventive  of  the  trouble. 

470.  Bathing.  —  A  noticeable  odor  of  perspiration  about 
any  part  of  the  body  is  a  sign  of  uncleanliness,  and  is  the 
best  indication  of  the  need  of  a  bath.  Even  in  cold  weather 
a  bath  is  needed  at  least  once  a  week,  while  in  the  summer 
it  may  be  necessary  to  bathe  daily.  Soap  and  hot  water 
soften  the  epithelium,  and  if  the  skin  is  then  rubbed  vigor- 
ously, a  large  amount  may  be  rolled  into  small  balls,  which 
are  often  supposed  to  be  dirt.  When  much  epithelium  is 
removed  in  this  way,  the  body  is  more  sensitive  to  the  cold, 


262  APPLIED   PHYSIOLOGY 

the  perspiration  passes  off  with  greater  ease,  and  the  skin 
is  made  tender. 

471.  Hot  baths.  — The  heat  of  a  bath  in  which  the  body- 
is  kept  warm  from  the  time  it  enters  the  water  until  it  is 
dry  dilates  the  blood  tubes  of  the  skin,  so  that  the  blood 
accumulates  upon  the  surface.  Thus  the  internal  organs 
contain  less  than  their  natural  supply  of  blood,  and  the 
body  is  apt  to  feel  weak  and  drowsy.  After  mental  labor 
a  hot  bath  may  cause  the  blood  to  leave  the  brain  and  so 
bring  about  sleep.  When  a  cold  is  coming  on,  a  hot  bath 
may  attract  blood  away  from  the  throat  and  bronchi  so 
that  the  inflammation  is  cut  short.  The  proper  time  for 
a  hot  bath  is  at  night,  just  before  retiring,  so  that  the  cir- 
culation may  become  natural  before  morning.  A  hot 
bath  requires  the  use  of  a  warm  room,  and  of  a  tub  suffi- 
ciently large  to  admit  most  of  the  body  at  once,  for  evap- 
oration of  the  warm  water  causes  a  cold  feeling  on  coming 
out  of  the  bath.  It  should  always  be  followed  by  rest  or 
sleep. 

472.  Cold  baths.  —  When  a  cold  bath  is  taken,  the  blood 
tubes  of  the  skin  at  first  contract  and  give  a  cold  feeling ; 
but  they  soon  dilate.  With  the  dilatation  there  comes  an  in- 
creased flow  of  blood  throughout  the  whole  body,  so  that 
there  is  a  feeling  of  warmth  and  vigor  in  marked  contrast 
with  the  drowsiness  of  the  hot  bath.  The  invigorating 
effects  of  a  bath  are  called  its  reaction.  If  a  cold  bath 
is  long  continued,  there  comes  on  a  second  contraction  of 
the  arteries,  so  that  the  blood  is  forced  within  the  body, 
producing  a  feeling  of  coldness  and  weakness  from  which 
the  body  is  a  long  time  in  recovering.  This  second  con- 
traction of  the  blood  vessels  is  called  the  secondary  reaction. 
The  bath  should  be  stopped  at  the  first  appearance  of  a 
chill. 


THE  SKIN   AND   BATHING  263 

473.  An  easy  way  of  bathing.  —  A  cold  bath  requires  nothing 
more  than  some  water  and  a  towel.  A  simple  wetting  of  the  body  with 
the  hands,  followed  by  rubbing  with  a  soft  towel,  produces  all  the  effects 
of  an  elaborate  bath  tub.  Such  a  bath  can  be  taken  in  two  minutes 
upon  rising  and  is  very  invigorating  and  refreshing. 

474.  Turkish  baths.  —  A  Turkish  bath  is  a  combination  of  hot 
and  cold  baths  in  which  the  body  at  first  is  made  to  perspire  in  a  hot 
bath  while  being  rubbed.  The  body  is  then  suddenly  deluged  with 
cold  water  and  rubbed  dry.  At  night  the  bath  is  refreshing,  but  the 
removal  of  epithelium  and  the  excessive  perspiration  make  the  bather 
liable  to  take  cold. 

475.  Sea  bathing.  —  Running  water  carries  off  the  heat  of  the 
body,  and  thus  produces  a  greater  effect  than  still  water.  The  motion 
of  the  waves  makes  sea  bathing  exhilarating,  and  the  salt  in  the  water 
seems  to  have  some  stimulating  effect. 

476.  Bathing  in  fevers.  —  A  cold  bath  always  lowers  the  tem- 
perature of  a  feverish  person,  and  if  properly  given,  greatly  adds  to  his 
comfort.  It  also  stimulates  the  skin  to  greater  activity  so  that  it  aids 
the  kidneys  in  their  work  of  excretion.  A  good  way  of  bathing  a 
feverish  person  is  to  uncover  only  an  arm,  and  wet  it  with  lukew^arm 
water.  Then  gently  rub  it  with  the  bare  hands  until  it  is  dry.  The 
evaporation  rapidly  produces  an  agreeable  coldness,  while  the  rub- 
bing keeps  up  the  circulation  and  prevents  taking  cold.  Then  cover 
it  and  go  over  the  other  arm,  and  then  the  legs,  and  the  body  in 
the  same  way.  Finish  by  washing  the  face  and  brushing  the  teeth. 
It  is  proper  to  give  such  baths  several  times  a  day  if  the  fever  is 
high. 


SUMMARY 

The  skin   consists   of    a   thick  network  of  connective 

tissue,  called  the  derma,  covered  with  several  layers 

of  epithelium,  called  the  epideiinis. 
A  hair  is  formed  by  the  welding  together  of  epithelium 

in  a  minute  tube  in  the  skin. 
Sebaceous  glands  pour  an  oily  substance  upon  the  hair 

roots  to  soften  the  skin  and  hair. 


264  APPLIED   PHYSIOLOGY 

4.  At  the  backs  of  the  ends  of  the  fingers  and  toes  the 

epitheUum  is  thickened  and  hardened  to  form  the 
nails. 

5.  Digestive  disturbances  are  the  principal  causes  of  a 

poor  complexion. 

6.  Paints  and  powders  irritate  the   skin  and   have  the 

same  effect  as  dirt. 

7.  Daily  brushing  the   hair  and  frequently  washing  it 

with  soap  and  water  are  the  best  means  of  keep- 
ing it  soft  and  glossy. 

8.  Nails  should  be  smoothly  trimmed,  and  gently  cleaned. 

9.  The  skin  should  be  washed  often  enough  to  prevent 

an  odor  of  perspiration. 

10.  The  heat  of  hot  baths  dilates  the  arteries  of  the  skin 

so  that  blood  leaves  the  internal  organs  and  brain 
and  produces  a  feeling  of  rest  and  drowsiness. 

11.  A  cold  bath  contracts  the  arteries  of  the  skin.     But 

they  soon  dilate  and  produce  a  feeling  of  warmth 
and  exhilaration,  called  the  reaction. 

12.  If  a  cold  bath  is  continued,  the  arteries  again  contract, 

producing  chilliness  and  a  feeling  of  exhaustion. 

DEMONSTRATIONS 

112.  Examine  a  specimen  of  skin  with  a  microscope.  Notice  the 
network  of  connective  tissue  in  the  derma,  and  the  numerous  arteries 
and  veins.  Notice  its  projections  of  papillae  and  their  covering  of 
epithelium.  Notice  that  the  epithelial  cells  in  the  deepest  layers  are 
large  and  round,  and  the  outermost  layers  are  flat  and  shriveled  and  can 
scarcely  be  recognized.  Notice  a  faint  line  of  colored  granules  in  the 
third  or  fourth  layer  of  cells.  In  a  negro  the  colored  layer  is  very  dis- 
tinct. The  specimen  will  also  probably  show  one  or  two  winding  sweat 
glands. 

113.  The  skin  specimen  will  prol)ably  show  a  few  hairs,  but  one 
specially  prepared  will  be  better.     Notice  the  deep  tubclike  depression 


THE  SKIN   AND   BATHING  265 

in  which  the  hair  rests,  and  the  Httle  knob  embraced  by  the  hair  at  its 
bottom.  Notice  the  whitish  cells  of  the  sebaceous  glands  reaching  off 
from  the  side  toward  which  the  hair  points.  Underneath  the  gland  will 
likely  be  seen  the  faint  outlines  of  the  small  muscle  which  causes  the 
hair  to  stand  on  end. 

114.  A  specimen  of  nail  under  the  microscope  will  appear  almost 
transparent,  but  the  papillae  of  the  skin  and  the  young  epithelial  cells 
beneath  it  will  show  well. 

115.  Wash  a  boy's  arm.  Then  apply  a  cloth  wet  in  hot  water  for 
a  few  minutes  and  show  how  the  softened  epithelium  can  be  rubbed 
off.     Explain  that  it  is  not  dirt,  but  the  protection  of  the  arm. 

REVIEW  TOPICS 

1.  Describe  the  skin,  its  derma,  epidermis,  subcutaneous 

tissue,  and  coloring  matter. 

2.  Describe  the  modifications  of  epidermis  in  a  callous 

spot  and  a  corn. 

3.  Describe  freckles  ;  a  blister ;  an  ulcer. 

4.  Describe  the  papillae. 

5.  Describe  a  hair,  sebaceous  glands,  and  blackheads. 

6.  Describe  the  nails. 

7.  Give  the  causes  and  treatment  of  a  bad  complexion, 

and  the  effects  of  paints  and  powders  and  drugs. 

8.  Give  simple  directions  for  the  care  of  the  hair. 

9.  Give  simple  directions  for  the  care  of  the  nails. 

10.  Give  a  general  rule  when  to  bathe  for  cleanliness. 

1 1.  State  the  effects  of  a  hot  bath,  and  when  to  take  it. 

12.  State  the  effects  of  a  cold  bath,  and  give  a  simple  and 

easy  way  of  taking  one. 

13.  Describe  a  Turkish  bath,  and  give  reasons  for  not  soak- 

ing and  rubbing  the  skin  to  an  excessive  degree. 

14.  Give  an  easy  way  of  bathing  a  feverish  person. 


CHAPTER   XXVIII 

NERVES 

477.  Uniformity  of  cell  action.  —  Certain  cells  forming 
the  nervous  system  are  set  apart  for  purpose  of  command- 
ing the  rest  to  work  in  the  proper  time  and  manner.  The 
commanding  cells,  called  7ierve  cells,  form  the  essential 
part  of  the  brain  and  spinal  cord.  From  them  as  a  center, 
fine  threads  called  nerves  run  to  the  cells  of  the  body. 
The  outer  end  of  each  nerve  thread  touches  a  company  of 
cells  and  carries  to  them  the  orders  from  the  central  nerve 
cells.  Although  each  cell  in  the  body  lives  and  acts  inde- 
pendently of  the  rest,  yet  the  central  nerve  cells  cause  all 
to  act  in  harmony. 

478.  Nerves.  —  Each  nerve  thread  is  composed  of  a 
central  fiber  surrounded  by  a  protective  layer  of   a  kind 

of  fat.     The  whole 


thread  is  only  about 


TKWci  ii^ch  in  diam- 
A  nerve  thread  ( x  400) .  *  u  w  u 


a   central  conducting  fiber.  b    covering  of  fat. 


eter.  Those  which 
go  to  each  part  of 
the  body,  as  a  hand  or  leg,  run  together  in  a  bundle,  which 
divides  into  its  separate  threads  upon  reaching  its  destined 
part.  Each  bundle  of  nerve  threads  is  usually  called  a 
nerve.  The  main  nerves  of  the  arms  are  about  the  size 
of  knitting  needles,  while  the  great  sciatic  nerve  of  the 
leg  is  as  large  as  the  end  of  the  little  finger. 

266 


NERVES 


267 


As  a  general  rule,  a  large  nerve  accompanies  an  artery  down  the 
inside  of  each  limb  and  across  the  center  of  joints  upon  the  side  toward 
which  the  limb  is  bent.  Thus  they  are  in  protected  positions.  One 
nerve  cord  is  situated  on  the  inside  of  the  back  of  the  elbow  joint 
and  is  called  ih.&  funny  bo?ie.  Owing  to  its  unusual  position,  it  is  some- 
times hit,  producing  a  pain  in  its  ending  on  the  inside  of  the  hand. 


479.  Nerve  action. — When  one  of  the  main  nerves  of 
the  arm  is  irritated,  as  by  a  pinch  or  prick,  or  shock  of 
electricity,  an  impulse  is  started  along  the  nerve  in  each 
direction.  It  goes  to  the  brain 
and  produces  a  sejisation  either 
of  pain  or  pleasure.  It  also 
goes  to  the  muscle  cells  of  the 
arm,  causing  them  to  contract 
and  move  the  arm.  If  a  nerve 
is  cut  and  the  end  nearest  the 
brain  is  irritated,  a  sensation 
will  be  felt,  but  there  will  be 
no  motion.  If  the  other  cut 
end  is  irritated,  the  muscles 
will  move  the  arm,  but  no  feel- 
ing whatever  will  be  produced. 

Whether  the  nerve  be  irritated  at  its  outer  endings 
at  the  cells  or  anywhere  in  its  course,  an  influence  will 
travel  to  the  central  nerve  cells  carrying  the  news,  and 
also  in  the  opposite  direction  to  the  cells  of  the  body, 
causing  them  to  act.  The  cells  of  the  body  can  originate 
influences  which  travel  up  the  nerve  to  the  central  nerve 
cells ;  and,  on  the  other  hand,  the  nerve  cells  can  origi- 
nate influences  which  travel  to  the  cells  of  the  body  and 
cause  them  to  act.  Transmitting  impulses  is  the  essential 
duty  of  nerves.  They  may  be  compared  to  telephone 
wires  which  transmit  any  kind  of  electrical  influences  over 


A  thin  slice  from  the  end  of  a  cut 
nerve  (x  200). 

a  nerve  thread. 

b   connective     tissue     binding     the 
threads  into  a  cord. 


268  APPLIED   PHYSIOLOGY 

their  whole  length  without  affecting  anything  in  their 
course. 

480.  Kinds  of  nerves.  —  Each  thread  of  a  nerve  trans- 
mits influences  in  only  one  direction.  Some  threads  carry 
influences  only  from  the  cells  of  the  body  to  the  central 
nerve  cells.  Because  they  often  produce  sensation  they 
are  called  sejisory  nerves.  Other  threads  carry  orders  for 
action  from  the  nerve  cells  to  the  cells  of  the  body  and 
are  called  motor  nerves.  Most  nerves  are  made  up  of 
both  sensory  and  motor  threads,  but  some  are  wholly  sen- 
sory and  others  wholly  motor.  There  is  no  difference  in 
their  appearance. 

481.  Distribution  of  sensory  nerves.  —  Nearly  every  cell  in 

the  body,  except  in  the  epidermis  and  blood,  is  probably  in  connection 
with  a  sensory  nerve,  and,  through  it,  is  in  touch  with  the  central  nerve 
cells.  The  endings  of  the  nerves  are  so  abundant  in  the  skin  just 
beneath  the  epithelium,  that  the  point  of  a  fine  needle  cannot  be  thrust 
in  without  producing  pain.  In  the  ends  of  the  fingers  they  are  more 
numerous  than  in  any  other  part  of  the  body.  The  muscles  and  internal 
organs  have  fewer  sensory  nerves  than  the  skin,  so  that  a  cut  may  be 
continued  into  the  deeper  parts  with  but  little  pain. 

482.  Kinds  of  sensations.  —  The  cells  are  continually 
sending  impulses  to  the  central  nerve  cells  telling  of 
their  needs,  as  of  food  or  rest.  These  impulses  often  give 
rise  to  feelings  which  may  seem  to  pervade  the  whole  body. 
Then  they  are  called  com^noii  seitsations.  Some  are  pleas- 
ant and  some  are  disagreeable.  The  natural  unreasoning 
incHnations  to  gratify  desires  aroused  by  the  needs  of  the 
body  are  instincts. 

When  something  outside  the  body  is  acting  upon  the 
nerves  it  produces  a  feeling  or  impression  of  which  a  per- 
son is  usually  aware.  By  means  of  these  sensations  the 
mind  forms  definite  ideas  of  the  surroundings  of  the  body, 


NERVES  269 

and  so  the  feelings  are  called  special  sensations.  Unlike 
common  sensations,  the  meaning  of  the  sensations  must 
be  learned. 

483.  Common  sensations.  —  Hunger,  thirst,  and  fatigue 
are  the  usual  common  sensations  felt  by  the  mind. 
Hunger  seems  to  be  located  in  the  stomach.  If  a  sub- 
stance swallowed  is  not  nutritious,  hunger  soon  returns, 
even  if  the  organ  is  filled  full.  On  the  other  hand,  if 
nutritious  food  is  introduced  into  the  body  through  the 
intestine,  the  feeling  of  hunger  will  pass  away,  even 
though  the  stomach  remains  empty.  Some  persons  suffer- 
ing from  indigestion  are  always  hungry,  though  they  eat 
enormously.  But  the  food  is  not  digested,  and  does  not 
reach  the  cells,  and  there  is  always  a  feeling  of  hunger. 

Thirst  seems  to  be  located  in  the  mouth.  Moistening 
the  mouth  allays  it  but  for  a  moment  only,  while  if  water 
is  introduced  into  the  intestine  or  veins,  the  thirst  disap- 
pears, even  though  the  mouth  receives  no  water. 

The  amount  of  common  sensations  is  small  compared 
with  similar  impulses  which  we  do  not  feel.  Every  cell 
is  continually  sending  tiny  messages  of  its  needs,  and  the 
central  nerve  cells  promptly  respond. 

484.  Special  sensations.  —  Knowledge  of  the  outside 
world  is  gained  by  means  of  the  touch,  sight,  hearing, 
smell,  and  taste.  Of  these,  touch  is  located  in  all  parts 
of  the  body,  while  special  organs  are  needed  to  enable  the 
nerves  to  catch  the  delicate  impressions  of  sight,  sound, 
smell,  and  taste. 

485.  Sensations  of  touch.  —  When  an  object  touches 
the  epithelium  of  the  skin,  it  causes  an  impulse  to  travel 
to  the  central  nerve  cells  as  a  sensation  either  of  touch, 
temperature,  pain,  or  weight.  All  these  sensations  are 
included  under  the  general  term  of  touch.     Touch  proper 


2/0  APPLIED   PHYSIOLOGY 

is  a  slight  sensation  caused  by  contact  of  the  skin  with  an 
object.  By  means  of  it  such  ideas  as  those  of  shape, 
smoothness,  size,  and  dampness  are  gained. 

Different  parts  of  the  body  vary  greatly  in  the  ability  of  their  nerves 
to  detect  sHght  differences  between  two  sensations.  Thus  the  ends  of 
the  fingers  distinctly  feel  two  points  yV  inch  apart  as  separate  points, 
while  if  two  points  are  applied  to  the  back,  they  seem  as  one  point 
until  they  are  separated  two  inches.  So  we  naturally  use  the  ends 
of  the  fingers  to  feel  with. 

486.  Sensations  of  temperature. — In  the  skin  special 
nerves  seem  to  end  in  minute  points  which  are  situated 
from  ^  to  -^  of  an  inch  apart.  When  these  are  touched,  a 
sensation  of  heat  or  cold  is  felt,  while  the  skin  between 
feels  only  a  touch  or  pain.  Some  spots  give  a  sensation 
of  cold  only,  and  others  of  heat  only. 

Sensations  of  extreme  heat  or  of  extreme  cold  cease  to  be  feelings  of 
temperature,  but  are  felt  only  as  pain.  The  skin  is  so  sensitive  that  it  can 
detect  a  difference  of  i  of  a  degree  of  temperature  between  two  objects. 

487.  Painful  sensations. — A  sensation  of  touch  or  of 
temperature,  if  greatly  increased  or  often  repeated,  be- 
comes unpleasant  and  is  called  a  pain.  The  same  sensa- 
tion may  be  felt  at  one  time  as  a  pleasant  touch  and  at 
another  as  a  pain.  When  an  influence  is  becoming  great 
enough  to  endanger  the  body,  it  arouses  the  nerves  of 
pain  and  produces  a  strong  and  unpleasant  feeling  which 
overpowers  the  simple  sensation  of  touch  and  compels  us 
to  withdraw  from  the  danger.  Pain  is  a  protection  for  the 
body  and  not  altogether  an  evil  or  a  punishment.  When 
the  nerves  of  pain  in  an  arm  or  leg  are  diseased,  the 
limb  may  be  burned  beyond  recovery  without  a  person's 
knowledge.  In  many  diseases  pain  is  a  prominent  symp- 
tom, and  the  physician  is  besought  to  give  it  relief.    Yet  he 


NERVES  271 

hesitates  before  giving  morphine,  knowing  that  to  reheve 
the  pain  is  to  mask  the  danger  signals  so  that  he  cannot 
judge  of  the  real  cause  of  the  trouble. 

Tickling  is  a  sensation  between  touch  and  pain.  It  is  produced  in 
parts  which  are  poorly  supplied  with  nerves  of  touch,  as  on  the  back  or 
the  neck.  At  first,  tickling  is  a  pleasant  sensation,  but  if  continued, 
it  becomes  extreme  suffering.  Some  persons  and  animals  who  are  able 
to  endure  great  pain  are  unable  to  control  themselves  when  tickled 

Itching  is  a  sensation  which  is  overcome  by  producing  a  greater 
sensation  in  the  part,  as  by  scratching.  Although  itching  is  usually 
only  an  annoyance,  in  a  greater  degree  it  is  a  torment  even  worse  than 
pain,  and  may  lead  a  person  to  injure  the  skin  seriously  by  deep 
scratching. 

488.  The  muscular  sense.  —  Sensations  of  weight  or  of 
resistance  are  judged  partly  by  the  amount  of  muscular 
effort  needed  to  move  the  body,  and  so  depend  in  large 
part  upon  the  motor  nerves.  But  the  feelings  of  pressure 
upon  the  body  and  of  muscular  effort  aid  in  producing  the 
sensation.  An  object  lifted  seems  distinctly  heavier  if  its 
weight  is  increased  only  ^V,  while  if  it  is  placed  upon 
the  skin,  its  weight  must  be  increased  \  before  it  feels 
heavier. 

489.  Necessity  of  epithelium.  —  The  covering  of  epithelium 
not  only  protects  the  nerves  from  injury,  but  also  modifies  an  impulse 
which  produces  a  sensation,  so  that  it  is  spread  over  a  larger  area  of 
nerves  and  is  made  a  gentle  instead  of  a  painful  sensation. 

490.  Motor  nerves.  —  Besides  touching  a  sensory  nerve, 
each  cell  probably  communicates  with  a  motor  nerv^e  also. 
Motor  nerves  begin  at  the  central  nerve  cells  and  end  at 
the  cells  of  the  body.  Over  them  the  central  nerve  cells 
send  orders  based  upon  information  brought  by  the  sen- 
sory nerves.  Many  orders  are  sent  by  willful  efforts  of  a 
person,  but  by  far  the  most  are  sent  without  our  knowledge. 


2/2  APPLIED    PHYSIOLOGY 

Motor    impulses   are   of    three   kinds,  —  for    motion,    for 
secretion,  and  for  growth. 

491.  Impulses  producing  motion.  —  The  action  of  every 
muscle  cell  depends  upon  an  impulse  brought  from  the 
central  nerve  cells  by  its  motor  nerve.  When  these  influ- 
ences are  cut  off,  there  is  pm^alysis  of  the  part,  so  that  no 
amount  of  willful  effort  can  cause  the  muscles  to  move  the 
limb.  The  peristalsis  of  the  intestine  and  the  beating  of 
the  heart  are  caused  by  influences  brought  to  their  muscle 
cells  by  motor  nerves.  Orders  for  movements  of  which 
we  know  nothing  are  far  greater  in  amount  than  those 
sent  to  voluntary  muscles. 

492.  Impulses  producing  secretion.  —  Secretion  is  also 
dependent  upon  orders  brought  to  the  glands  by  motor 
nerves.  For  example,  when  food  is  taken  into  the  mouth, 
the  sensory  nerves  carry  the  news  to  the  nerve  cells,  which 
at  once  send  out  an  order  along  the  motor  nerves  to  the 
salivary  glands  to  produce  more  saliva.  If  the  nerves  are 
cut,  only  a  little  saliva  will  be  produced,  while  if  the  end 
in  connection  with  the  gland  is  irritated,  the  gland  will 
respond  with  a  greater  quantity  of  saliva.  In  the  same 
way  the  secretion  of  all  glands  is  controlled. 

493.  Influences  producing  growth. — When  the  motor 
nerve  to  a  part  is  cut,  the  cells  will  be  inactive,  and,  as  it 
were,  too  lazy  even  to  eat.  So,  unless  continually  under 
the  influence  of  motor  nerves,  the  cells  become  weak  and 
waste  away.  When  the  cells  of  a  part  are  much  used, 
impulses  are  sent  causing  them  to  take  in  more  nourish- 
ment, so  that  they  increase  in  size  and  strength.  Thus  a 
muscle  becomes  larger  and  stronger  by  use.  During  the 
action  of  a  muscle  its  motor  nerves  also  bring  orders  for 
the  arteries  to  dilate  and  carry  more  blood  to  feed  the 
working  part. 


NERVES  273 

494.  Rate  of  transmission  of  nerve  impulses.  —  Ordinary 

sensations  travel  about  100  feet  per  second.  This  is  about  the  rate  of 
the  fastest  express  trains,  but  our  arms  are  so  short  that  pain  seems  to 
follow  an  injury  instantly.  In  some  diseases  the  rate  is  very  much 
retarded,  so  that  if  the  hand  should  happen  to  rest  upon  a  hot  stove 
it  would  be  badly  burned  before  the  sensation  would  travel  to  the  brain 
and  give  warning  of  the  danger. 

495.  A  sensation  traveling  over  a  nerve  seems  to  come  from  its 
beginning.  When  the  funny  bone,  or  nerve  that  winds  around  the 
back  of  the  elbow,  is  pinched,  the  little  finger  side  of  the  hand,  where 
the  nerve  ends,  feels  as  if  pricked  by  needles.  When  an  arm  or  a  leg 
is  cut  off,  and  the  nerves  in  the  stump  are  irritated,  a  pain  is  felt  which 
seems  to  be  in  the  lost  limb.  When  a  nerve  is  pressed  upon,  it  may 
be  partly  paralyzed  for  a  while.  Then  the  part  which  it  supplies 
becomes  less  sensitive  and  is  moved  with  difficulty.  At  the  same 
time  an  impulse  caused  by  the  irritation  of  the  pressure  produces  a 
sensation  which  seems  to  the  brain  to  come  from  the  end  of  the  nerv^e. 
Thus  when  sitting  crosslegged  the  foot  often  seems  asleep  and  full  of 
needles,  while  it  is  itself  insensitive  when  touched. 

A  cut  nerve  will  become  whole  again,  but  it  takes  some  weeks.  In 
the  meantime  the  parts  supplied  by  the  nerve  cannot  feel  or  move. 

496.  Diseases  of  the  nerves.  —  Nerves  may  become  inflamed, 
producing  the  disease  called  neuritis.  Then  there  will  be  great  pain  and 
tenderness  over  the  entire  course  of  the  nerve.  In  severe  cases  there  will 
be  paralysis  and  loss  of  feeling.    The  disease  is  very  slow  in  its  course. 

Sciatica  is  a  mild  but  painful  form  of  inflammation  in  the  main  nerve 
of  the  leg.  Inflammation  of  the  nerves  may  be  caused  by  rheumatism  or 
malaria,  but,  above  all,  by  alcohol. 

497.  Effect  of  alcohol  upon  nerves.  -—  A  little  alcohol 
seems  to  hasten  the  rate  of  transmission  of  nervous  im- 
pulses by  increasing  the  circulation  of  the  blood,  but  a 
few  drinks  retard  their  action.  A  great  danger  of  using 
alcohol  is  that  it  may  cause  neuritis  or  inflammation  of  the 
nerves.  Slow,  steady  drinking  may  produce  it  as  well  as 
occasional  sprees.  It  comes  without  warning,  but  remains 
a  long  while,  producing  pain  and  paralysis.  Alcohol  pro- 
duces the  disease  as  often  as  all  other  causes  combined. 

OV.  PHYSIOL. —  18 


2/4  APPLIED   PHYSIOLOGY 

SUMMARY 

1.  The  cells  of  the  body  are  made  to  act  harmoniously  by 

means  of  orders  sent  from  a  few  cells  in  a  central 
lie I'v oils  sy stein. 

2.  A  nerve  is  a  bundle  of  microscopic  threads,  each  run- 

ning from  a  central  nerve  cell  to  the  cells  of  the 
body. 

3.  Nerves  transmit  impulses  caused  by  irritation  from  out- 

side the  body,  and  also  impulses  originated  in  either 
the  cells  of  the  body  or  the  central  nerve  cells. 

4.  Sensory  nerves  carry  from  the  cells  news  concerning 

a  substance  which  is  touching  the  body,  and  they 
inform  the  central  nerve  cells  when  the  cells  are  tired 
or  are  in  need  of  food. 

5.  Motor  nerves  carry  orders    to  the  cells   to  move,  to 

secrete,  to  eat,  and  to  grow. 

6.  Impulses  in  nerves  travel  about  100  feet  per  second. 

7.  Nerves  may  become  inflamed   and   produce  pain  and 

paralysis. 

8.  Alcohol   often    produces   severe    inflammation   of    the 

nerves. 

DEMONSTRATIONS 

1 16.  Skin  the  leg  of  a  small  animal  or  frog,  and  push  apart  the 
muscles  upon  the  inside  of  its  upper  part.  White  nerve  cords  will  be 
seen  to  lie  alongside  the  main  artery  and  vein,  and  can  be  traced  up- 
ward to  the  spinal  cord  and  downward  until  they  become  lost  in  the 
skin  or  muscles.  Notice  that  those  which  branch  off  to  the  skin  are  as 
large  and  numerous  as  those  which  supply  all  the  rest  of  the  leg. 
Notice  how  much  force  is  needed  to  break  one  of  the  nerves.  In 
ancient  times  it  was  supposed  that  tendons  and  nerves  were  the  same. 
Compare  a  nerve  with  a  tendon  to  see  their  points  of  resemblance. 

117.  To  show  the  effect  of  irritating  a  nerve  in  its  course,  pinch  a 
boy's  funny  bone.     He  will  wonder  how  the  sensation  travels  to  the 


NERVES  275 

brain  when  he  feels  it  go  down  to  his  little  finger.     Explain  that  it 
only  seems  to  come  from  the  finger,  but  does  not  go  there. 

118.  With  a  power  of  at  least  200  diameters,  show  specimens  of  a 
nerve  mounted  for  the  microscope.  In  a  specimen  of  nerve  cut  length- 
wise, notice  the  slender  conducting  fiber  running  down  the  middle  of 
each  thread  and  its  thicker,  clear  covering  of  fat.  In  a  specimen  cut 
across  the  nerve,  notice  that  the  conducting  fiber  of  each  nerve  thread 
appears  as  a  central  dot  within  a  circle  of  the  protecting  fat.  Notice 
the  fine  connective  tissue  between  the  threads.     Sketch  the  specimen. 

119.  Show  the  difference  in  sensibility  of  different  parts  of  the  skin 
by  touching  it  with  the  points  of  a  pair  of  compasses.  Upon  the  balls 
of  the  fingers  the  points  will  seem  separate  even  if  near  together,  while 
upon  the  back  they  will  seem  one  when  separated  two  inches. 

120.  Show  that  some  parts  of  the  skin  feel  sensations  of  temperature 
more  than  the  others  by  drawing  the  point  of  a  lead  pencil  slowly 
across  the  cheek.  At  intervals  there  will  be  felt  a  cold  sensation,  show- 
ing that  a  special  nerve  of  temperature  has  been  touched. 

121.  Cut  a  nerve  in  a  recently  killed  frog  and  separate  it  from  the 
flesh  for  a  short  distance.  After  a  moment,  pinch  the  nerve,  and 
the  muscles  will  contract. 

REVIEW  TOPICS 

1.  Describe  the  essential  parts  of  the  nervous  system. 

2.  Describe  a  nerve. 

3.  Explain  the  two  results  of  irritating  a  nerve. 

4.  Define  and  name  the  kinds  of  sensory  impulses. 

5.  Describe  the  sensations  of  touch,  pain,  temperature, 

and  weight. 

6.  Tell  how  the  cells  make  known  their  wants. 

7.  Show  how  epithelium  aids  the  sense  of  touch. 

8.  Name  and  describe  the  three  kinds  of  motor  impulses. 

9.  Give  the  rate  of  transmission  of  impulses  along  nerves. 

10.  Describe  the   effects  of   pressure   upon   a  nerve ;    of 

cutting  a  nerve ;  and  of  disease  of  a  nerve. 

11.  Tell  how  alcohol  affects  a  nerve. 


CHAPTER   XXIX 


THE   SPINAL   CORD 


498.  The  first  collection  of  central  nerve  cells  is  in  the 
spinal  cord.  The  spinal  cord  is  a  soft  white  cylinder  of 
nervous  tissue,  about  half  an  inch  in  diameter.  It  is 
securely  hung  in  the  upper  two  thirds  of  the  tube  formed 
by  the  bony  rings  of  the  backbone.  It  extends  from  the 
bottom  of  the  skull  to  about  the  level  of  the  lowest  rib,  a 
length  of  about  eighteen  inches.  It  is  only  about  two 
thirds  as  large  as  its  tube,  and  so  is  not  likely  to  be  injured 
by  bending  the  backbone. 

499.  The  gray  matter.  —  When  the  cord  is  cut  across, 
the  central  part  of  its  end  shows  the  grayish  outline  of  a 

butterfly  surrounded  by  a 
thick  layer  of  a  whiter 
substance.  The  gray  mat- 
ter is  a  collection  of  nerve 
cellsy  which  give  off  nu- 
merous nerve  fibers  like 
the  central  fibers  of  ordi- 
nary nerve  threads.     The 

A  thin  slice  from  the  spinal  cord  with  the  ^^^jg  ^^^  ^^^^^^  1  ^f  ^^ 
cells  and  nerves  magnified  200  diameters.  V-, 

,    .  inch  in  diameter.     Some 

a  cells  m  the  gray  matter. 

b   fibers  in  the  gray  matter.  of    the    nerVC    fibers    COm- 

c    nerve  threads  in  the  white  matter.  n^unicatC  with    Other  Cclls 

of  the  cord,  and  some  take  coverings  and  become  ordinary 
nerve  threads.  The  whole  is  bound  together  by  delicate 
connective  tissue. 

276 


THE   SPINAL  CORD 


277 


The  spinal  cells  receive  a  part  of  every  impulse  from  the 
sensory  nerves,  and  take  part  in  sending  out  motor  impulses 
to  the  various  parts  of  the  body. 

500.  The  white  matter.  —  The  white  matter  is  made  up 
of  nerve  fibers  which  still  retain  their  coverings.  In  fact, 
the  white  matter  is  simply  a  huge  nerve.  The  nerve 
threads  of  the  white  matter  adjoining  the  right  and  left 
sides  of  the  gray  matter  are  motor  threads  carrying  im- 


FRONT    SIDE 


Diagram  of  the  action  of  each  part  of  the  spinal  cord. 

pulses  from  the  brain  to  the  cells  of  the  gray  matter.  The 
nerve  threads  outside  of  these  and  the  threads  behind  the 
gray  matter  are  prolongations  of  the  sensory  nerves  of  the 
body,  some  of  which  finally  go  to  the  brain,  and  others 
connect  with  the  cells  of  the  gray  matter  of  the  cord. 

501.  Spinal  nerves.  —  The  spinal  cord  gives  off  thirty- 
one  pairs  of  nerves  through  openings  between  the  rings 
of  the  backbone.  Each  nerve  is  made  of  a  sensory 
and  of  a  motor  part  which  soon  unite  into  a  single 
bundle  in  which  the  two  kinds  of  nerves  cannot  be  dis- 


2/8 


APPLIED   PHYSIOLOGY 


tinguished.     These  spinal  nerves  supply  the  whole  body 
below  the  neck. 

502.    Action  of  nerve  cells  in  voluntary  motion.  —  The 

spinal  cells  do  not  originate  impulses  or  act  of  their  own 

accord,  but  they  act  only  when 
ordered  to  do  so  by  the  brain 
or  when  the  cells  of  the  body 
express  a  need  of  protection, 
nutrition,   or  rest.      When   a 

a  motor  nerve  root  from  the  front  part     pCrSOn  wishcS  tO  lift  his  hand, 

of  the  nerve. 
b  sensory   nerve   root   from   the   back 

part  of  the  cord. 
c  gray  matter  of  the  cord. 
d  white  matter. 


Diagram  of  the  origin  of  nerves  in 
the  spinal  cord. 


his  brain  sends  an  order  to 
these  nerve  cells,  and  they  in 
turn  send  the  order  over  the 
nerves  to  the  muscles  which 
move  the  hand.  In  this  way  the  mind  sends  all  orders 
for  voluntary  motion.  For  each  muscle  there  is  a  sepa- 
rate group  of  spinal  cells.  If  these  cells  are  injured  or 
destroyed,  a  person  cannot  move  his  muscles  voluntarily. 


Diagram  of  reflex  action. 

a  tack  pricking  the  hand.  b  sensory  nerve.  c  nerve  cell  in  the  spinal  cord. 

d  motor  nerve.         e  muscle  moving  the  hand. 


503.  Reflex  action.  —  The  spinal  cells  also  send  out 
orders  in  response  to  impulses  brought  by  sensory  nerves. 
Motor  impulses  sent  in  response  to  influences  brought  by 


THE  SPINAL  CORD  2/9 

sensory  nerves  are  reflex  acts.  Reflex  action  is  designed 
to  protect  the  body  from  injury  and  to  supply  its  needs. 
Most  acts  of  the  cord  are  reflex.  When  the  finger  touches 
a  hot  object,  the  sensory  nerves  carry  the  sensation  to  the 
cells  of  the  spinal  cord  and  to  the  brain.  Before  the  sen- 
sation reaches  the  brain,  the  spinal  cord  sends  out  an  order 
for  the  muscles  to  move  the  finger  away  from  the  heat. 
The  brain  becomes  conscious  of  the  burn  and  of  the  move- 
ment of  the  finger  at  about  the  same  time.  In  this  way 
the  spinal  cord  protects  the  body  against  all  kinds  of 
injuries. 

504.  Reflex  action  in  relation  to  nutrition.  —  Digestion 
is  mainly  a  reflex  act.  Motor  impulses  for  glands  to  pro- 
duce the  digestive  juices  are  sent  out  from  the  spinal  cord 
when  the  sensory  nerves  bring  word  that  food  is  present 
in  the  stomach  or  intestine.  Peristalsis  is  also  a  reflex  act 
.dependent  upon  the  presence  of  food.     The  sensory  nerves 

also  carry  to  the  spinal  cells  news  of  the  temperature  of 
a  part  and  of  its  need  of  more  or  of  less  blood,  and,  in 
response,  the  cells  send  out  motor  impulses  for  the  arteries 
to  change  their  size.  The  heart  is  also  somewhat  affected 
in  a  reflex  way.  The  sensations  of  exertion  and  fatigue 
are  carried  to  the  spinal  cells,  which  send  out  orders  for 
more  rapid  heart  beats.  Fear,  joy,  anger,  and  sorrow  all 
affect  the  heart  in  a  reflex  way. 

The  growth  of  each  separate  cell  is  controlled  by  the  same  set 
of  spinal  cells  that  produce  motion  in  a  part.  Muscle  cells,  especially, 
need  the  constant  stimulus  of  the  spinal  cells  to  keep  them  growing,  for 
otherwise  they  slowly  waste  away  and  become  weak.  The  spinal  cord 
is  continually  overseeing  the  nutrition  and  gro\vth  of  cells,  and  if  it 
were  to  cease  its  oversight,  their  death  would  soon  take  place. 

505.  Reflex  action  in  habitual  movements.  —  The  reflex 
action  of  the  cord  aids  in  performing  simple  movements  of 


280  APPLIED   PHYSIOLOGY 

the  body.  The  peculiar  sensations  which  tell  a  man  that 
he  is  beginning  to  fall  pass  to  the  cells  of  the  cord,  and 
they  in  a  reflex  way  send  out  the  proper  orders  for  the 
muscles  to  put  the  body  in  an  upright  position  again. 

506.  Reflex  action  in  education.  —  The  reflex  action  of 
the  spinal  cord  can  be  educated.  Even  a  simple  reflex 
action  like  standing  must  be  learned.  When  a  baby  first 
tries  to  walk,  his  brain  cells  give  the  proper  orders  to  the 
cells  of  the  spinal  cord,  and  they  in  turn  give  them  to  the 
muscles.  Thus  he  slowly  directs  each  detail  of  the  move- 
ments with  his  brain.  Soon  the  spinal  cord  learns  to  send 
the  next  order  as  soon  as  it  feels  the  sensation  of  the 
previous  movement,  and  finally  all  the  movements  needed 
become  reflex,  and  the  child  runs  about  with  but  little 
effort  on  the  part  of  his  brain. 

In  learning  to  play  a  piano,  the  brain  is  occupied  both  in  reading 
the  notes  and  directing  the  movements  of  the  fingers  in  playing. 
But,  at  last,  the  brain  has  only  to  read  the  notes  to  the  cord  and  it 
instantly  sends  the  proper  orders  that  they  be  played. 

Education  and  skill  in  any  art  consist  in  the  ability  of  the  cord  to 
execute  proper  movements  while  the  brain  is  wholly  occupied  with  the 
design.  In  this  ability  to  acquire  new  uses,  the  cells  of  the  nervous 
system  differ  from  all  other  cells  of  the  body.  When  the  hand  is 
educated,  it  is  really  the  spinal  cells  which  are  educated. 

507.  Excessive  reflex  action.  —  Reflex  acts  are  some- 
times not  beneficial.  A  slight  noise  gives  some  people  a 
fright,  and  in  lockjaw  the  slightest  sensation  causes  the 
spinal  cells  to  send  out  orders  for  the  muscles  of  the  body 
to  contract  violently.  Self-control  is  largely  the  power 
which  the  brain  has  of  restraining  the  spinal  cells  from 
sending  out  orders  even  when  strong  and  sudden  sensa- 
tions are  received.  Thus,  when  something  tickles  the 
throat,  it  is  possible  for  the  brain  to  restrain  the  spinal 


THE  SPINAL  CORD  28 1 

cells  from  sending  the  order  to  cough.  In  the  same  way 
men  sometimes  endure  great  pain  without  shrinking. 

508.  Broken  back.  —  Injuries  to  the  backbone  may- 
injure  the  spinal  cord  so  that  it  cannot  conduct  nervous 
influences  past  the  injured  point.  Then  parts  of  the  body- 
below  the  point  of  injury  can  neither  send  nor  receive 
messages  from  the  brain,  but  are  paralyzed  both  in  sensa- 
tion and  motion.  Yet  the  reflex  action  of  the  part  may 
persist,  for  the  part  of  the  cord  below  the  injury  still 
retains  its  vitality. 

509.  Disease  of  the  spinal  cord.  —  There  are  diseases 
which  may  destroy  the  action  of  any  single  part  of  the 
cord  or  of  the  whole  cord  below  the  seat  of  the  disease. 
Then  there  will  be  loss  of  sensation  or  of  motion  or 
impairment  of  nutrition,  usually  in  the  lower  part  of  the 
body.  The  diseases  are  generally  slow  in  their  course  and 
incurable. 

510.  The  action  of  the  cord   is   unconscious.  —  The  cord 

ahvays  acta  wholly  without  a  person's  knowledge.  Like  a  faithful 
nurse,  it  stands  guard  over  the  cells  of  the  body  and  controls  them  in 
their  nutrition,  growth,  and  work.  The  brain  restrains  its  excessive 
action  and  directs  it  in  ordering  the  voluntary  movements,  but  leaves 
to  it  almost  the  entire  care  of  individual  cells. 

SUMMARY 

1.  The  spinal  cord  is  made  up  of  a  central  mass  of  gray 

matter  surrounded  by  white  matter. 

2.  The  gray  matter  is  made  up  of  cells  from  which  nerve 

fibers  extend  both  to  the  brain  and  to  the  cells  of  the 
body. 

3.  The  white  matter  is  composed  of  nerve  threads  which 

connect  the  cells  of  the  cord  with  the  brain  and  with 
the  nerves  of  the  body. 


282  APPLIED   PHYSIOLOGY 

4.  Thirty-one  pairs  of   nerves  connect  the  cord  with  all 

parts  of  the  body. 

5.  The  use  of  the  cells  is  to  send  orders  over  the  motor 

nerves  when  told  to  do  so  by  the  brain,  and  also 
to  send  orders  in  response  to  information  brought 
to  them  by  sensory  nerves. 

6.  Orders  sent  in  response  to  sensations  are  reflex  acts. 

7.  Reflex  acts  are  for  protection,  nutrition,  and  to  relieve 

the  brain  from  the  drudgery  of  sending  orders  for 
every  detail  of  bodily  movements. 

8.  The  reflex  action  in  an  educated  spinal  cord  enables  a 

person  to  work  with  skill. 

9.  Restraint  of  excessive  reflex  acts  constitutes  self-control. 

DEMONSTRATIONS 

122.  Procure  a  spinal  cord  at  the  butcher's.  Notice  the  nerves 
going  off  from  the  cord.  Notice  how  the  cord  is  enveloped  by  a  thick, 
fibrous  sheath  and  is  held  in  place  by  the  nerves  and  fibrous  bands. 
Remove  the  cord  from  the  bone  and  slit  open  its  sheath.  Notice  the 
soft  consistency  of  the  cord  and  its  shape  like  two  cords  pressed 
together.  On  its  clean-cut  edge  notice  the  grayish  butterfly-shaped 
center  and  the  pure  white  outer  part. 

123.  Examine  a  thin  cross  section  of  the  cord  under  the  microscope 
with  at  least  200  diameters.  In  the  outer  parts  of  the  specimen  notice 
the  round  circles  of  cut  nerve  threads.  Explain  that  this  is  the  white 
matter  of  the  cord. 

Examine  the  central  part,  noticing  the  large  nerve  cells  and  nerve 
fibers  which  run  in  all  directions.  Notice  the  fine  and  wavy  connective 
tissue  fibers  binding  the  whole  together. 

124.  The  pure  reflex  action  of  the  cord  can  be  shown  with  a  decapi- 
tated frog.  Place  a  small  piece  of  blotting  paper,  wet  with  a  strong 
acid,  upon  its  back,  and  it  at  once  kicks  it  off"  with  its  hind  leg.  Prick 
its  back,  and  it  makes  one  leap.  Suspend  it  with  its  hind  legs  hanging 
down,  and  let  a  toe  touch  a  dish  of  acid,  and  it  at  once  draws  up  the 
leg.     (See  demonstration  35.) 

Explain  that  the  frog  has  no  feeling  or  sense,  but  performs  the  move- 


THE   SPINAL  CORD  283 

ments  in  a  reflex  way  to  escape  danger  in  the  same  way  that  a  boy 
suddenly  jumps  when  he  touches  a  sharp  pin. 

125.  To  show  reflex  action,  have  a  boy  sit  with  one  knee  crossed 
over  the  other  and  hanging  perfectly  limp.  Now  strike  the  front  of 
the  knee  just  below  the  patella.  The  thigh  muscles  will  contract  and 
cause  the  leg  to  kick.  This  will  succeed  best  if  the  boy  is  not  looking 
when  you  strike. 

REVIEW  TOPICS 

1.  Describe  the  spinal  cord;  its  appearance  and  situation; 

its  gray  matter,  its  white  matter,  and  the  origin  of 
the  nerves  which  arise  from  it. 

2.  Describe  how  the  cells  of  the  gray  matter  act  in  caus- 

ing voluntary  movements,  and  in  causing  reflex 
movements. 

3.  Explain  how  reflex  action  is  a  protection  to  the  body ; 

how  it  controls  all  processes  of  the  growth  and  secre- 
tion of  the  cells ;  and  how  it  enables  a  person  to 
acquire  skill  in  movements. 

4.  Explain  how  reflex  acts  may  be   harmful;    how   self- 

control  may  overcome  the  harm. 

5.  Describe  the  effects  of  injury  to  the  spinal  cord. 

6.  Describe  the  effect  of  diseases  of  the  spinal  cord. 


CHAPTER  XXX 

THE  SYMPATHETIC  NERVOUS  SYSTEM 

511.  Of  what  the  system  consists. — The  spinal  cord  con- 
trols the  contraction  of  the  arteries,  the  peristalsis  of  the 
intestine,  and  the  growth  of  cells.  Yet  the  impulses  which 
it  sends  out  for  these  purposes  pass  through  another  set 
of  nerve  cells  and  nerves  called  the  sy^npathetic  nervous 
system. 

The  sympathetic  nervous  system  consists  of  small  bodies 
like  grains  of  corn  or  smaller,  called  ganglia,  from  which 
nerves  go  out  in  all  directions.  There  are  four  main  pairs 
of  ganglia  in  the  head,  and  twenty-three  in  a  row  down 
the  front  of  the  backbone  all  connected  by  nerves.  Each 
ganglion  is  a  collection  of  nerve  cells  and  nerve  fibers 
bound  together  by  connective  tissue.  Nerve  threads  con- 
nect its  cells  with  the  cells  of  the  spinal  cord  and  also  with 
the  muscle  cells  of  the  arteries  and  intestine.  Through 
the  arteries  they  probably  affect  all  the  cells  in  the 
body.  The  nerve  threads  are  smaller  than  those  of  ordi- 
nary nerves,  and  seldom  form  bundles  large  enough  to  be 
seen.  They  usually  consist  of  a  fiber  like  the  central  fiber 
of  an  ordinary  nerve  thread  without  its  fatty  covering. 
They  are  thus  not  easily  found  even  with  the  aid  of  a 
microscope. 

The  nerves  from  the  ganglia  run  mainly  along  the 
course   of   the   large    arteries.      Upon    the   aorta  and   its 

284 


THE  SYMPATHETIC  NERVOUS   SYSTEM  285 

main  branches  in  the  chest  and  abdomen,  nerves  and  small 
ganglia  form  intricate  networks,  each  called  a  plexus. 

Just  back  of  the  stomach  there  is  a  large  and  important 
plexus  called  the  solar  plexits,  whose  nerves  supply  the 
muscles  of  the  organs  of  the  abdomen.  A  plexus  within 
the  heart  controls  the  action  of  the  heart. 

512.  Sensory  sympathetic  nerves.  —  The  sympathetic 
nerves  carry  both  sensory  and  motor  impulses,  but  only 
faint  impulses  of  pain  and  touch.  Thus  the  circulation 
of  the  blood  and  digestion  of  food  go  on  almost  without 
our  knowledge,  but  a  very  strong  irritation  may  give  rise 
to  an  abdominal  pain,  as  in  colic. 

Sensory  impulses  telling  of  the  wants  of  the  cells  and  of 
the  need  of  secretion  or  movements  of  the  arteries  or  digest- 
ive organs  are  continually  being  received  by  the  ganglia. 
These  impulses  travel  slowly  and  require  some  time  to 
produce  an  impression.  Most  of  them  travel  only  to  the 
cells  in  the  ganglia,  and  few  get  farther  than  to  the  cells 
in  the  spinal  cord.  Only  very  strong  impressions,  whose 
cause  may  injure  the  body,  reach  the  brain  and  produce  a 
feeling  of  pain,  hunger,  thirst,  or  fatigue. 

513.  Motor  sympathetic  nerves.  —  The  ganglia  send 
orders  to  the  epithelial  cells  of  the  glands  to  produce 
their  secretions,  and  to  the  muscles  of  the  intestine  and 
arteries  either  to  contract  or  to  dilate.  They  do  this  in 
response  to  information  furnished  by  the  sensory  nerves. 
They  also  send  out  orders  for  the  growth  and  nutrition 
of  the  cells  of  the  body  on  receipt  of  news  of  their  needs. 
Most  orders  from  the  ganglia  are  reflex. 

514.  Mode  of  action  of  the  ganglia. — If  cut  off  from  connec- 
tion with  the  cord,  the  ganglia  send  few  impulses.  The  cord  seems 
to  furnish  them  with  a  supply  of  nervous  energy.  They  seem  to  take 
a  small  amount  of  its  active  impulses  and  transform  it  into  a  large 


286  APPLIED   PHYSIOLOGY 

amount  of  gentle  impulses  for  the  arteries  and  intestine.  When  poisons 
or  spoiled  food  irritate  the  intestine  to  a  dangerous  degree,  the  sensa- 
tion goes  beyond  the  ganglia  and  excites  the  spinal  cells  to  action.  In 
response  they  send  out  direct  orders  which  cause  energetic  and  painful 
peristalsis  to  remove  the  food,  in  marked  contrast  with  the  gentle  action 
caused  by  the  ganglia  alone. 

515.  Influence  of  the  brain.  —  The  brain  has  some  power  over 
the  ganglia.  Excitement  or  fear  may  influence  the  spinal  cord  so  that 
it  in  turn  modifies  the  impulses  going  through  the  ganglia.  Sorrow 
seems  to  depress  the  ganglia  so  that  the  processes  of  digestion  and 
assimilation  are  not  so  well  performed,  and  the  nutrition  and  growth  of 
the  cells  of  the  body  are  diminished.  But  nature  has  arranged  that  after 
leaving  the  brain,  mental  influences  shall  act  through  two  sets  of  nerve 
cells  before  'they  can  directly  aifect  the  nutrition  of  the  body.  Thus 
man^s  body  is  protected  against  injury  from  his  ever-changing  moods. 

516.  Connection  of  organs  with  each  other.  —  By  means  of 

the  sympathetic  system,  a  nervous  influence  in  one  organ  is  spread  over 
all  the  rest.  Because  other  organs  seem  to  share  in  the  sickness  when 
one  is  deranged,  the  nerves  controlling  them  are  called  sympathetic 
nerves.  Thus,  when  one  organ  is  deranged,  the  others  act  less  strongly 
and  impose  less  work  upon  the  disabled  part. 

517.  Injury  to  sympathetic  nerves. — The  sympathetic 
nerves  are  less  influenced  by  outside  impressions  than  any 
other  nerves  in  the  body,  and  great  violence  is  needed  to 
impair  their  action  seriously.  Poisons  which  are  swallowed 
or  produced  during  disease  may  injure  them  so  that  the 
ganglia  almost  cease  to  send  out  their  orders.  Then  life  is 
endangered,  and  strong  nerve  stimulants  like  strychnine 
are  needed. 

Aside  from  poisons,  almost  the  only  grave  danger  which 
may  threaten  the  sympathetic  system  is  a  blow  upon  the 
abdomen  or  neck.  A  hard  blow  or  great  pressure  just 
below  the  ribs  may  paralyze  the  solar  plexus.  The  arteries 
then  enlarge  and  hold  so  much  blood  that  too  little  goes 
to  the  head  and  brain.  So  there  is  danger  of  sickness  and 
of  death.     A  blow  upon  the  side  of  the  neck  may  injure 


THE   SYMPATHETIC  NERVOUS   SYSTEM  28/ 

the  large  ganglia  which  are  situated  there,  as  well  as 
the  large  nerves  near  by,  and  make  such  a  profound 
impression  upon  the  heart  that  death  may  take  place 
at  once.  Blows  upon  the  neck  or  abdomen  are  always 
dangerous. 

SUMMARY 

1.  The    sympathetic    nervous    system    consists   of   collec- 

tions of  nerve  cells  called  ganglia,  and  of  both 
sensory  and  motor  nerves  which  follow  the  course 
of  the  arteries. 

2.  The  cells    of   the    spinal   cord    send   impulses   to   the 

ganglia,  and  they  in  turn  distribute  them  to  the 
arteries  and  glands  and  to  the  organs  of  the  chest 
and  abdomen. 

3.  The  ganglia  send  orders  only  in  a  reflex  way  accord- 

ing to  impressions  received  from  their  sensory 
nerves. 

4.  The  ganglia  control  the  contraction  and  dilatation  of 

the  arteries,  the  peristalsis  of  the  intestine,  the  secre- 
tion of  glands,  and  the  growth  of  the  cells  of  the 
body. 

5.  The  ordinary  sensory  impulses  conducted  by  the  sym- 

pathetic nerves  produce  no  feeling. 

6.  The  heart  is  controlled  mainly  by  a  set  of  small  ganglia 

within  its  own  walls. 

7.  The    sympathetic    system    produces   slow   and    gentle 

movements  in  contrast  with  the  quick  and  active 
movements  made  by  the  spinal  cord. 

8.  The  brain  has  no  direct  control  over  the  ganglia. 

9.  Blows  upon  the  neck  or  abdomen  may  injure  the  sym- 

pathetic nerves  so  as  to  cause  death. 


288  APPLIED   PHYSIOLOGY 


REVIEW  TOPICS 

1.  Describe  the  sympathetic  nervous  system:  its  ganglia, 

nerves,  plexus,  and  its  connection  with  the   spinal 
cord. 

2.  Describe    the    sensory   impulses    of    the    sympathetic 

nerves. 

3.  Describe  its  motor  impulses  and  their  relation  to  the 

arteries ;    to  secretion  of  glands ;    to   peristalsis ;    to 
the  growth  of  cells,  and  to  the  heart. 

4.  Describe  how  the  ganglia  send  out  their  impulses. 

5.  Describe  how  the  spinal  cord  has  influence  over  the 

ganglia,   and   how  they  work  independently  of  the 
cord. 

6.  Describe  how  the  brain  can  affect  the  ganglia. 

7.  Describe  how  the  action  of  the  ganglia  may  be  seriously 

impaired  by  injuries. 


CHAPTER   XXXI 

THE  BRAIN 

518.  General  structure.  —  The  brain  is  the  part  of  the 
central  nervous  system  which  can  originate  orders  in  dis- 
tinction from  the  spinal  cord,  which  acts  only  in  response 


Brain  of  a  frog ;  top  view  ( x  lo) , 

a   cerebrum. 

d   optic  tubercles. 

c   cerebellum. 

d  medulla. 

e    upper  end  of  spinal  cord. 


Brain  of  a  hen ;  side  view  (X  2). 

a  cerebrum. 
b   optic  nerve. 
c   optic  tubercle. 
d  medulla. 
e    cerebellum. 
/  spinal  cord. 


to  impulses  brought  to  it.  In  reptiles,  toads,  and  frogs,  it 
is  very  simple  in  structure,  but  yet  contains  parts  corre- 
sponding to  all  the  parts  of  the  brain  of  man.  In  them  the 
spinal  cord  swells  out  to  form  a  cone-shaped  body  called 
the  medulla  oblongata.     Above  it  there   is  a   small  flat 


ov.  PHYSIOL. — 19 


289 


290  APPLIED   PHYSIOLOGY 

swelling  called  the  cerebellum,  the  next  two  smaller  bodies 
called  the  optic  tiibe^xles,  and  at  the  top  two  larger  bodies 
which  together  are  called  the  cerebnim.  They  follow 
each  other  in  a  straight  line.  In  man  the  parts  are  bent 
upon  each  other,  while  the  cerebrum  is  so  large  that  it 
covers  all  the  other  parts. 

519.  Coverings.  —  The  brain  of  man  is  a  very  soft  body 
weighing  about  fifty  ounces.  It  is  contained  in  the  top  of 
the  skull.  It  is  covered  with  a  delicate  network  of  fibers 
called  the  pia  mater,  which  carries  the  numerous  blood 
tubes  of  the  brain.  Outside  of  the  pia  mater  is  a 
thick,  tough  membrane  called  the  dura  mater.  The  dura 
mater  is  the  periosteum  of  the  inside  of  the  skull. 

520.  The  medulla.  —  The  upper  end  of  the  spinal  cord 
becomes  enlarged  into  a  wedge-shaped  body  called  the 
■medulla  oblongata,  or  simply  the  medulla.  The  medulla 
is  about  one  inch  and  a  quarter  in  length  and  three  quarters 
inch  in  breadth  at  its  upper  end.  Its  center  is  gray  matter 
covered  with  white  matter,  both  of  which  are  direct  con- 
tinuations of  the  same  matter  in  the  cord. 

521.  Nerves  of  the  medulla.  —  From  the  medulla  there 
go  out  seven  pairs  of  nerves  to  supply  the  head  and  face. 
They,  together  with  five  other  pairs  which  the  brain  gives 
off,  arc  called  cranial  nerves,  in  distinction  from  the  spinal 
nerves.  The  cranial  nerves  which  arise  in  the  medulla 
are  sensory  and  motor,  and  supply  the  head  and  face  just 
as  the  spinal  nerves  do  the  rest  of  the  body.  They  con- 
nect with  cells  in  the  medulla  which  act  only  in  a  reflex 
way.  In  this  sense,  the  medulla  is  a  part  of  the  spinal 
cord,  and  not  of  the  brain.  One  of  these  seven  cranial 
nerves  is  partly  a  nerve  of  the  special  sense  of  taste. 
Impressions  of  hearing,  sight,  and  smell  are  carried  by 
three  cranial  nerves  arising  higher  up  in  the  brain. 


THE   BRAIN  29I 

522.  The  vagus  nerve.  —  One  of  the  pairs  of  cranial  nerves  is 
called  the  vagus,  or  pneiunogasU'ic,  nerve.  It  supplies  a  small  sensory 
branch  to  the  ear,  and  motor  branches  to  the  larynx  and  pharynx ; 
then  it  passes  into  the  thorax  and  gives  off  branches  to  the  heart, 
which  restrain  its  action.  It  gives  sensory  branches  to  the  esophagus 
and  lungs,  and  finally  reaches  the  stomach  and  liver.  The  main  nerve 
supply  of  these  organs  is  from  the  spinal  cord,  or  from  the  sympathetic 
svstem,  but  the  vagus  nerve  is  an  additional  means  for  better  resulatino- 
their  action  to  suit  the  needs  of  the  body. 

523.  Centers  originating  impulses.  —  In  the  medulla,  a 
collection  of  nerve  cells,  called  the  respiratory  ce7iter, 
sends  out  a  regular  succession  of  orders  for  respiratory 
movements.  While  the  orders  may  be  hastened  or  re- 
tarded by  other  nerve  centers  to  suit  the  needs  of  the 
body,  yet  the  medulla  compels  the  respiratory  muscles  to 
act  so  as  to  keep  the  body  supplied  with  sufficient  oxy- 
gen. Thus  it  is  a  real  part  of  the  brain.  When  the 
respiratory  center  is  destroyed,  respiration  and  life  cease 
instantly. 

There  is  another  part  of  the  medulla,  called  the  vaso- 
motor center,  which  controls  the  contraction  of  arteries, 
and  another  which  regulates  the  peristalsis  of  the  esoph- 
agus in  swallowing.  While  these  are  partly  reflex  acts, 
yet  their  perfect  action  requires  original  impulses  to  be 
sent  from  the  medulla. 

524.  Effects  of  reflex  influences.  —  The  respiration,  circula- 
tion of  the  blood,  and  taking  of  food  are  essential  vital  processes  of 
life  which  the  medulla  controls  without  our  being  aware  of  it.  Strong 
influences  from  the  nerves  of  the  body  may  act  in  a  reflex  way  to 
modify  the  impulses  of  the  medulla.  Great  fear  may  cause  the  vaso- 
motor center  to  send  out  impulses  for  the  contraction  of  the  arteries  so 
as  to  produce  great  paleness.  Instances  have  occurred  in  which  the 
disturbance  of  circulation  from  this  cause  has  produced  death. 

525.  Effects  of  injury.  — An  injury  to  the  respiratory  and  vaso- 
motor centers  causes  death  at  once.     A  broken  neck,  if  high  up,  may 


292 


APPLIED   PHYSIOLOGY 


involve  the  medulla  and  cause  instant  death.      But  the   medulla   is 
so  situated  that  only  the  greatest  violence  can  harm  it. 

526.  The  cerebellum.  —  Just  above  and  overhanging  the 
medulla  is  a  rounded  mass  called  the  cerebellum.  It  forms 
less  than  one  fifth  of  the  brain.     It  consists  of  an  interior 

white  mass  of  nerve 
threads,  covered  with 
a  layer  of  gray  matter 
about  ^^5-  of  an  inch  in 
thickness.  On  the  sur- 
face are  deep  fissures 
into  which  the  gray 
matter  dips,  so  that  its 
amount  is  greatly  in- 
creased. In  the  gray 
matter  are  nerve  cells 
which  are  connected 
with  the  rest  of  the  nervous  system  through  the  nerves 
of  its  white  matter.  These  nerve  cells  are  the  essential 
part  of  the  cerebellum.  They  have  no  connection  with 
any  vital  process  of  life,  and  do  not  take  part  in  thought. 
A  man  with  a  diseased  cerebellum  can  perform  a  single 
muscular  act  like  raising  his  hand,  but  he  cannot  direct 
changing  and  complicated  movements,  such  as  are  required 
in  writing,  walking,  or  balancing  his  body.  Thus  the  cere- 
bellum acts  like  a  balance  wheel,  so  that  orders  for  com- 
plicated movements  may  be  sent  with  regularity  and  pre- 
cision. 

527.  The  optic  tubercles.  —  The  optic  tubercles  are  two  small 
collections  of  gray  matter  situated  upon  the  main  nerve  tracts  which 
connect  the  cerebrum  and  medulla.  They  seem  to  be  connected  with 
the  reflex  movements  of  the  eye.  Other  collections  of  gray  matter  near 
them  seem  also  to  be  connected  with  the  eye. 


^- 


Diagram  of  a  human  brain. 

a   cerebrum.        b  cerebellum.        c  medulla. 


THE  BRAIN 


293 


Cells  from  the  gray 
matter  of  the  cerebrum 
(X  300). 


528.  The  cerebrum.  —  The  main  nerve  tract,  after  pass- 
ing through  the  spinal  cord,  medulla,  and  optic  tubercles, 
spreads  out  to  form  a  mass  called  the 
cei'ebrum.  While  in  frogs  and  fishes  it 
is  no  larger  than  the  medulla  or  optic 
tubercles,  in  man  it  forms  more  than 
four  fifths  of  the  whole  brain  and  over- 
hangs all  the  other  parts. 

It  consists  of  a  central  mass  of  nerve 
threads  covered  with  a  layer  of  gray 
matter  one  eighth  of  an  inch  in  thick- 
ness, containing  numerous  large  cells.  Each  cell  gives  off 
numerous  fine  fibers.  Most  of  these  fibers  form  an  intri- 
cate network  among  the  cells,  but  one  from  each  cell  takes 
a  covering  and  becomes  a  nerve  thread  of  the  white  mat- 
ter, and  finally  reaches  other  cells  of  the  brain  or  even  of 
the  spinal  cord. 

529.  Fissures  of  the  brain.  —  The  cerebrum  is  divided 
nearly  into  two  parts,  called  hemispheres,  by  a  deep  furrow 

running  forward  and 
backward  upon  the  mid- 
dle of  its  upper  surface. 
Another  furrow,  called 
the  Sylvian  fissure,  starts 
near  the  bottom  of  the 
fore  part  of  the  side  of 
the  cerebrum  and  runs 
backward  and  upward. 
Many  other  furrows  and 
fissures  from  one  quarter 
to  one  half  inch  in 
depth,  run  in  waving  lines  between  its  main  furrows,  throw- 
ing its  surface  into  folds  called  convolzitiofis.     The  convo- 


Human  brain  cut  crosswise. 


294 


APPLIED   PHYSIOLOGY 


lutions  increase  the  surface  of  the  cerebrum,  so  that  in  all 
it  measures  about  four  square  feet.  This  greatly  increases 
the  area  over  which  the  nerve  cells  in  the  gray  matter  may 
be  spread.  The  interior  of  the  cerebrum  is  a  small  irregu- 
lar cavity,  called  the  ventricle,  which  is  filled  with  a  clear 
liquid. 

■>\    - — 


Regions  of  the  head  and  action  of  the  different  parts 
of  the  brain. 


530.  Regions  of  the  cerebrum.  —  The  fissures  and  con- 
volutions are  nearly  the  same  in  all  men,  and  mark  out 
definite  regions  upon  the  surface  of  the  brain.  First,  is 
the  region  just  behind  the  forehead,  called  the  frontal 
region.  Second,  is  the  region  lying  under  the  upper  part 
of  each  side  of  the  skull,  and  called  the  parietal  region. 
Third,  is  the  region  about  the  ear,  called  the  temporal 
region.    It  lies  just  above  and  in  front  of  the  ear.     Fourth, 


THE   BRAIN 


295 


that  part  of  the  brain  lying  under  the  back  of  the  skull 
is  called  the  occipital  region.  Each  region  of  the  brain 
does  a  special  work. 

531.  Action  of  the  cerebrum.  —  The  nerve  centers  may- 
act  reflexively  in  response  to  sensory  impulses,  as  the  spinal 
cord  usually  does ;  or  automatically  by  originating  their 
own  impulses,  like  the  respiratory  center  in  the  medulla 
and  the  nerve  cells  in  the  heart.  The  spinal  cord,  sym- 
pathetic system,  medulla,  and  cerebellum  all  act  in  one  or 
the  other  of  these  ways,  and  without  our  being  conscious 
of  their  action.  The  cerebrum  is  the  seat  of  the  thinking 
mind.  It  acts  in  an  automatic  way,  but  we  may  be  con- 
scious of  any  of  its  actions.  It  acts  first  by  feeling  sensa- 
tions; second  by  sending  orders  for  voluntary  muscular 
movements  ;  third,  by  thought.  It  does  each  kind  of  work 
in  a  particular  region  of  its  surface. 

532.  Sensory  regions.  —  Sensory  impressions  of  which 
we  are  conscious  are  sensations.  Sensations  of  hearing, 
smell,  and  taste  are  felt  by  the  temporal  region ;  of  sight 
by  the  occipital  region ;  and  of  touch  by  the  parietal  region. 
If  either  region  is  destroyed,  the  impressions  going  to  that 
area  are  no  longer  received,  and  the  person  is  devoid  of  the 
corresponding  sense.  Unless  each  impression  reaches  its 
own  region  of  the  surface  of  the  brain,  it  produces  no  sensa- 
tion, although  it  may  still  reach  reflex  centers  in  the  optic 
tubercles,  medulla,  or  cord,  and  give  rise  to  reflex  action. 

533.  Memory.  —  Impressions  may  be  retained  in  the  cells 
and  be  recalled.  These  constitute  memories.  Our  memo- 
ries are  complex  stores  of  impressions  in  widely  separated 
parts  of  the  brain.  The  sum  of  our  different  memories 
constitutes  a  great  part  of  our  knowledge. 

Different  regions  of  the  brain  are  connected  by  nerve 
fibers.     So  when   one  region   recalls  a  memory,  another 


296 


APPLIED    PHYSIOLOGY 


region  recalls  another  memory  of  the  same  object.     Thus, 
when  the  temporal  region  recalls  the  memory  of  a  sound 

of  a  bell,  the  occipital 
region  recalls  its  appear- 
ance. 

534.  Motor  regions.  — 
Orders  for  voluntary  mo- 
tion are  sent  by  the  cells 
lying  just  in  front  of  a 
zone  connecting  the  two 
ears.  Each  muscle  of 
the  body  is  controlled 
by  a  special  set  of  nerve 
cells  called  its  motor 
center. 

A  motor  impulse  passes 
down  through  the  white  mat- 
ter of  the  cerebrum,  medulla, 
and  spinal  cord  to  the  spinal 
nerve  cells,  and  then  out  along 
a  motor  nerve  to  a  muscle.  In 
an  injury  or  disease  in  the  top 
ceHs  of  the  cord," and  tends  "o  produce   of  the  skull  some  of  the  cells  of 


Diagram  of  the  course  of  nerve  influences 
in  voluntary  motions. 

a  object  to  be  picked  up. 

^   sensory  nerve. 

£    the  part  of  the  influence  which  goes  to  the 


the  motor  region  may  be  in- 
volved, giving  paralysis  of  cer- 
tain muscles.  By  the  muscles 
affected  one  can  often  judge 
of  the  exact  location  of  the 
trouble  and  remove  it  by  an 


reflex  action. 

d  cell  of  spinal  cord. 

e    motor  nerve  from  spinal  cord. 

f  continuation  of  the  sensory  nerve  3  up  the 
cord  to  the  brain. 

^  cell  of  the  brain  which  perceives  touch. 

A   motor  cell. 

z    thought  cell. 

J    motor  nerve  fiber  running  to  the  cells  of  the   operation. 

cord,  and  carrying  an  influence  which         535.     Relation       of      the 
continues  along  the  motor  nerve..  gensorv    tO    the    HlOtOr    re- 

Jk  muscle  which  moves  the  hand.  -' 

gions.  —  The  motor  and  sen- 
sory regions  are  in  close  connection  by  nerve  fibers  in  the  white  matter. 

The  motor  region  regulates  its  impulses  according  to  information  brought 


THE   BRAIN  297 

to  sensory  regions  by  sensory  nerves.  A  carpenter  regulates  the  force 
with  which  he  pushes  his  plane  according  to  the  feeling  of  muscular 
resistance. 

536.  Memory  of  movements.  —  Acts  of  motor  cells  are 
stored  in  memory  and  constitute  a  part  of  knowledge. 
All  motions  must  be  learned  at  first.  When  the  brain 
centers  have  learned  a  movement  thoroughly  they  teach 
the  spinal  centers  so  that  finally  their  work  is  almost  en- 
tirely relieved,  and  they  can  be  occupied  in  other  thoughts. 
Awkwardness  is  usually  the  result  of  the  brain's  attempt- 
ing to  send  out  orders  for  motion  while  it  is  occupied  with 
other  thoughts.  Ease  and  grace  of  motion  come  when  the 
spinal  centers  have  learned  to  relieve  the  brain  center. 

537.  Thought  regions.  —  The  cells  of  the  frontal  regions 
take  note  of  memories  stored  in  other  regions,  and  by  their 
comparison  form  new  ideas.  Thus,  a  pause  between  two 
sensations  or  mental  acts  gives  rise  to  an  idea  of  time ; 
and  the  sight  of  two  objects  removed  from  each  other  gives 
the  idea  of  space  and  of  number.  Neither  time  nor  space 
nor  number  in  itself  can  make  an  impression  upon  the 
senses,  and  yet  they  are  realities  in  the  mind.  Comparison 
of  memories  and  the  formation  of  new  ideas  is  tJiiiikinsr. 
Thoughts  themselves  are  stored  in  memory  and  can  be 
recalled  and  compared. 

538.  Speech.  —  Thought  is  expressed  by  speech.  By 
means  of  speech  new  sensory  and  motor  ideas  and  new 
thoughts  are  gained  and  stored  in  the  memory  without  the 
cells  of  the  different  regions  experiencing  the  particular 
sensations.  Herein  is  the  main  difference  between  a  man 
and  an  animal.  An  animal  gains  new  ideas  only  by 
memory  of  its  sensations  and  acts  which  it  itself  experi- 
ences, but  a  man  can  acquire  them  second  hand  by  being 
told.     Thus  a  man  may  be  profited  by  the  experience  of 


298  APPLIED   PHYSIOLOGY 

others.  Knowledge  gained  only  by  long  and  patient 
research  of  wise  men  is  imparted  to  children  in  a  few 
moments,  while  an  animal  can  impart  knowledge  only  in 
a  limited  degree. 

539.  Speech  in  animals.  —  All  animals  have  a  variety  of  natural 
cries.  Monkeys  have  a  dozen  separate  cries  which  are  similar  in  all 
species.  A  hen  has  at  least  five  different  cries  to  express  as  many 
different  ideas.  Parrots  and  crows  have  been  taught  to  speak  a  few 
words,  but  they  do  it  just  as  the  mocking  bird  or  brown  thrush  imitates 
any  sound  which  it  hears.     Speech  belongs  to  man  alone. 

540.  Of  what  speech  consists.  —  Speech  is  one  of  the 
highest  and  most  complicated  of  mental  processes.  It  is 
not  a  natural  gift,  but  must  always  be  learned  at  first. 
A  child  first  hears  a  word  spoken.  He  records  it  in  the 
temporal  regions  of  the  brain,  and  learns  to  recall  certain 
sensory  and  motor  memories  when  he  hears  the  word. 
By  the  time  he  is  a  year  and  a  half  old  his  motor  region 
begins  to  form  the  word  when  he  thinks  of  the  memory. 
At  the  age  of  six  or  eight  he  begins  to  recognize  the  printed 
word  with  his  sight  region,  and  finally  he  learns  to  write 
the  word  with  his  motor  region.  Thus  nearly  every  region 
in  the  brain  takes  part  in  some  form  of  speech. 

541.  Center  for  spoken  words.  —  The  muscles  of  the 
mouth  can  be  moved  by  the  cells  of  the  face  center  in  the 
motor  region,  but  their  movements  in  speech  are  so  precise 
and  complicated  that  a  center  is  especially  provided  to  pro- 
duce their  movements  in  talking.  It  is  situated  just  below 
and  in  front  of  the  motor  area,  but  is  usually  upon  only 
one  side.  When  this  center  is  disturbed,  a  person  cannot 
talk,  although  he  understands  spoken  and  written  speech, 
and  has  control  of  his  lips  and  tongue  in  doing  other  things. 

542.  Disturbance  of  the  speech  centers.  —  There  are  cases 
in  which  the  word-seeing  center  is  disturbed  so  that  a  person    can 


THE   BRAIN  299 

speak  and  write  correct  answers  to  questions,  but  cannot  read  and  un- 
derstand what  he  has  just  written.  Sometimes  a  person  cannot  speak 
his  thoughts,  but  can  read  aloud  what  he  has  written.  Careful  observa- 
tion of  the  speech  is  of  great  value  in  locating  brain  diseases,  for  the 
speech  centers  involve  nearly  every  region  of  the  brain. 

543.  Mind  study.  —  The  cerebral  cells  act  in  as  definite 
and  uniform  ways  as  the  cells  of  the  intestine  or  heart,  and 
men  studied  the  laws  of  their  minds  long  before  the  struc- 
ture or  even  the  existence  of  cells  was  known.  The  actions 
of  the  mind  are  divided  into  three  great  divisions.  First, 
is  the  intellect,  or  the  pure  knowledge-gaining  faculty.  This 
includes  the  work  of  all  the  sensory  regions  of  the  brain 
and  such  a  part  of  the  frontal  regions  as  is  concerned  in 
receiving  knowledge  through  speech.  It  is  the  basis  of  the 
other  mental  acts. 

544.  The  sensibilities. — The  second  division  of  mind 
study  comprises  the  sensibilities,  or  the  feelings.  Much 
of  knowledge  does  not  concern  us  in  the  least.  All  feeling 
is  based  on  knowledge,  and  all  knowledge  leads  up  to 
feeling  as  we  come  to  know  a  thing  intimately.  We  love 
it  or  hate  it,  and  are  sorry  for  its  loss. 

545.  The  will.  —  The  third  and  highest  act  of  the  mind 
is  to  will  to  do.  It  is  the  control  which  the  frontal  region 
has  of  the  motor  region.  In  order  to  do  a  thing  we  must 
first  have  knowledge,  and,  second,  we  must  feel  some  degree 
of  emotion  or  desire  to  do  it.  Only  a  small  part  of  knowl- 
edge causes  feeling  or  emotion,  and  only  a  small  part  of 
even  our  strong  feelings  are  expressed  in  action. 

Of  all  the  actions  of  the  mind  the  will  is  the  most  difficult  to  arouse 
and  control.  Since  it  depends  upon  feeling,  this  faculty  must  first  be 
aroused.  Men  readily  act  their  feelings  of  anger  and  fear.  To  form  a 
new  will,  active  and  brave,  which  is  capable  of  controlling  the  natural 
and  acquired  appetites  and  passions,  is  the  highest  and  noblest  work 
of  man. 


300 


APPLIED   PHYSIOLOGY 


546.  Brains  of  animals.  —  The  medulla  is  much  the  same  in 
all  animals  from  the  frog  up  to  man.  This  is  because  breathing  and  the 
flow  of  blood  are  much  the  same  in  all.  The  cerebellum  in  a  frog  or 
snake  or  fish  is  very  small,  for  they  need  but  a  small  regulating  and 
balancing  part.  A  bird  or  a  hen  must  make  precise  movements  in 
balancing  itself  in  flying  or  roosting,  and  so  it  has  a  large  cerebellum. 


Brain  of  an  ox. 

a  outline  of  brain  in  the  skull.       b   the  brain  removed  from  the  skull. 


The  optic  tubercles  of  frogs  and  birds  are  well  developed,  for  their  eyes 
are  perfect.  The  cerebrum  of  frogs  and  snakes  and  fishes  is  very  small. 
Its  hinder  parts  are  the  largest,  for  in  them  the  impressions  of  sight, 
hearing,  and  smell  are  located.  Its  fore  parts  are  mere  points,  as  would 
be  expected  from  the  low  intelligence  of  the  animals.  A  bird  has  a 
larger  cerebrum,  corresponding  to  a  greater  mind.  An  animal's  cere- 
brum is  much  larger  and  is  somewhat  folded  to  give  room  for  more 
nerve  cells,  but  the  frontal  or  thought  region  is  small.     An  animal's 


THE  BRAIN  301 

senses  are  as  acute  as  a  man's,  and  so  the  back  parts  of  its  brain  are 
well  developed. 

547.  Animal  intelligence.  —  An  animal  is  capable  of  storing 
sensory  and  motor  impressions  in  memory,  and  of  sending  out  motor 
impulses  according  to  sensory  impressions.  In  some  respects  he  is 
capable  of  doing  this  to  a  far  greater  extent  than  man.  For  instance, 
a  dog  can  find  his  master  by  the  sense  of  smell  alone.  He  can  also 
use  his  frontal  region  in  thought  and  judgment,  but  to  an  extent  which 
corresponds  to  the  small  size  of  this  region. 

548.  The  essential  difference  between  man  and  animals.  — 

The  possession  of  speech  seems  to  be  the  key  to  man's  progress  and 
noble  ambitions.  By  means  of  it  the  Creator  has  revealed  to  him  a 
knowledge  of  things  before  the  foundation  of  the  world,  and  of  things 
to  come.  Animals  are  incapable  of  receiving  instruction  except  through 
the  senses  and  so  they  make  no  progress.  Man  rises  in  thought  above 
time  and  space  itself. 

549.  The  nervous  system  in  lower  animals.  —  All  four- 
footed  animals,  birds,  fish,  and  reptiles  possess  nerves,  a  spinal  cord, 
and  a  brain.  Their  nerves,  sympathetic  system,  spinal  cord,  and 
medulla  are  developed  nearly  as  much  as  in  man,  for  the  creatures  eat, 
feel,  move,  and  breathe,  often  to  a  greater  extent  than  man.  The 
cerebrum  is  developed  according  to  the  intelligence  of  the  animal,  and 
the  cerebellum  according  to  the  complication  of  its  movements. 

Insects  and  worms  and  shellfish  have  no  brain  or  spinal  cord,  but 
a  row  of  ganglia  like  those  in  the  sympathetic  system  extends  through 
the  body.  Each  ganglion  gives  off  nerves  to  the  cells  of  the  body. 
These  creatures  do  little  else  than  eat  and  digest  food,  and  hence  the 
highest  nervous  system  is  not  needed. 

In  the  lowest  form  of  life  there  is  no  nervous  system  at  all.  When 
the  animal  consists  of  a  few  cells  or  of  only  a  single  cell,  no  nervous 
system  is  needed. 


SUMMARY 

1.  The  brain  is  the  part  of  the  central  nervous  system 

which  originates  impulses. 

2.  The   brain   is    continuous   with   the    spinal   cord,    and 

consists  of  the  medulla,  cerebellum,  optic  tubercles, 


302  APPLIED   PHYSIOLOGY 

and  cerebrum.  Each  consists  of  gray  matter  con- 
taining nerve  cells,  and  of  white  matter  made  of 
nerve  threads. 

3.  The  medulla  is  like  the  spinal  cord  in  that  it  gives  off 

sensory  and  motor  nerves. 

4.  The  medulla  also  originates  impulses  controlling  res- 

piration and  the  contraction  of  arteries. 

5.  The  cerebellum  adjusts  the  voluntary  motor  impulses 

of  the  brain,  so  that  movements  like  balancing  of 
the  body  are  done  with  precision. 

6.  The  optic  tubercles  are  reflex  centers  for  the  eyes. 

7.  The  cerebrum  forms  four  fifths  of  the  brain,  and  con- 

sists of  a  puckered  covering  of  gray  matter  over  a 
central  mass  of  white  nerve  fibers. 

8.  The  cells  of  each  part  of  the  brain  have  a  definite 

work  to  do.  They  receive  sensory  impressions, 
send  motor  impulses,  and  think. 

9.  The  impressions   of  each   cell  remain   as   permanent 

memories  which  can  be  recalled  at  will. 

10.  By  means    of    speech,   thought,    sensory    and   motor 

impressions  are  conveyed  to  other  persons  and  there 
become  memories  as  though  they  had  actually  been 
experienced. 

11.  In  speech  the  centers   for   motion,  sound,  and  sight 

all  take  part. 

12.  There  is  a  special  center  for  producing  the  movements 

of  the  mouth  in  speech. 

13.  The  first  stage  of  mind  action  is  knowledge  ;  the  next, 

emotion  ;  and  the  third,  willing  and  acting. 

DEMONSTRATIONS 

126.    Show  as  types  the  brains  of  a  frog  or  fish  ;  of  a  hen  ;  and  of  a 
fourfooted  animal.     A  frog's,  fish's,  or  chicken's  brain  can  easily  be 


THE  BRAIN  303 

removed  by  cutting  away  the  skull.  After  opening  the  top  of  the  skull, 
place  it  with  the  brain  in  Muller^s  fluid  or  formalin  for  a  few  days,  when 
the  brain  will  be  hard  and  can  be  removed  with  little  injury. 

127.  In  the  frog,  note  the  medulla,  then  the  thin  cerebellum,  look- 
ing like  a  disk  of  paper  with  its  edge  inserted  just  above  the  medulla. 
Note  the  swelling  optic  tubercles,  and  then  the  long,  pointed  halves  of 
the  cerebrum. 

Next  compare  the  same  parts  on  a  bird's  brain.  Note  the  similar 
medulla  and  optic  tubercles.  Note  the  large  cerebellum  forming  a  half 
moon  above  the  optic  tubercles,  and  marked  with  cross  fissures  upon 
its  back  part.  Note  the  cerebrum  in  front,  shaped  like  a  chestnut  and 
as  large  as  the  rest  of  the  brain. 

Next  compare  the  same  parts  in  a  mammaPs  brain.  Note  the  similar 
medulla,  but  the  larger  cerebellum.  The  optic  tubercles  are  obscured 
by  the  cerebrum.  Note  the  cerebrum,  large  enough  to  cover  almost 
all  the  rest  of  the  brain.     Note  the  convolutions. 

Now  compare  these  brains  with  a  model  or  a  picture  of  the  brain 
of  man.  Note  the  large  frontal  regions  in  man  and  the  larger  and 
more  numerous  fissures  and  convolutions,  and  that  the  cerebrum  com- 
pletely covers  all  the  other  parts  of  the  brain. 

128.  When  the  skull  of  an  animal  is  opened,  note  the  lining  of  tough 
and  thick  dtcra  7naier,  which  may  be  peeled  off  with  little  difficulty. 
Note  that  it  extends  in  between  the  two  hemispheres  of  the  brain  and 
between  the  cerebrum  ^nd  cerebellum.  Underneath  it,  note  the  deli- 
cate meshes  of  the  pia  mater,  containing  numerous  blood  tubes.  Note 
that  it  dips  into  all  the  fissures  and  contains  a  small  amount  of  a  thin, 
clear  fluid. 

129.  Examine  a  specimen  of  the  gray  matter  of  the  cerebrum  or 
cerebellum  with  a  microscope  magnifying  400  diameters.  Note  its  nerve 
cells  with  fine  branches.  The  white  matter  will  appear  like  a  collection 
of  ordinary  nerve  fibers.     Sketch  the  specimen. 


REVIEW  TOPICS 

1.  Name  the  different  parts  of  a  frog's  brain  in  order, 

and  tell  how  they  differ  from  the  same  parts  in  a 
man's  brain. 

2.  Describe  the  two  coverings  of  the  brain. 


304 


APPLIED  PHYSIOLOGY 


3.  Describe  the  medulla,  its  nerves  and  reflex  action ; 

its  respiratory  center ;   its  vasomotor  center ;   and 
the  effects  of  its  injury. 

4.  Describe  the  cerebellum  and  give  its  action. 

5.  Describe  the  optic  tubercles  and  give  their  action. 

6.  Describe  the  cerebrum  ;  its  hemispheres,  fissures,  con- 

volutions, gray  and  white  matter,  and  regions. 

7.  Locate  the  region  in  which  impressions  of  sight  are 

received;  of  touch;    of  hearing;  of  smell;  and  of 
taste. 

8.  Describe  the  region  from  which  motor  impulses   for 

voluntary  motion  are  sent  out. 

9.  Describe  the    memory,   and  show  why  recalling  one 

thought   brings   to   mind    another   thought  of   the 
same  object. 

10.  Locate  the  thought  region  of  the  brain,  and  describe 

the  process  of  thought. 

11.  ShovV  that  by  speech  man  gains  ideas  which  an  animal 

can  get  only  by  actual  experience. 

12.  Locate  and  describe  the  mode  of  action  of  the  center 

for  spoken  words ;   for  written  speech ;  and  of  the 
speech-hearing  and  speech-seeing  centers. 

13.  Describe  the  three  main  divisions  of  the  acts  of  the 

mind. 

14.  Compare  the  corresponding   parts    of   the  brains   of 

different  animals  with  each  other  and  with  the  same 
parts  of  the  brain  of  man. 

15.  Describe  the  nervous  system  in  insects,  worms,  shell- 

fish, and  in  the  lowest  forms  of  animals. 


CHAPTER    XXXII 
INFLUENCES   WHICH  AFFECT   THE  MIND 

550.  Stimulation  to  action.  —  The  thought  cells  of  the 
brain  are  given  power  over  voluntary  actions  of  the  body, 
with  no  higher  power  to  cause  them  to  act,  except  the  will, 
which  is  the  result  of  their  own  action.  Were  a  child  left 
entirely  to  itself,  it  would  probably  exercise  its  mind  no 
more  than  an  animal.  But  the  sight  of  objects  and  ambi- 
tions not  yet  attained  spurs  the  thought  cells  to  action, 
just  as  sensations  cause  the  spinal  cord  and  motor  region 
to  act.  Without  constant  stimulus  of  the  senses  and  feel- 
ings the  thought  cells  languish  and  almost  cease  to  act. 
As  the  body  is  compelled  to  grow  by  the  cells  of  the  spinal 
cord,  so  must  the  mind  be  compelled  to  grow  by  an  effort 
of  the  will.  Few  men  possess  a  will  strong  enough  to  act 
without  the  stimulus  of  other  minds,  but  association  with 
trained  minds  arouses  the  will  to  exercise  one's  own  mind. 

551.  Concentration  of  the  mind.  —  In  order  to  become 
educated,  the  mind  must  be  exercised  persistently  and  for 
hours  at  a  time.  The  mind  does  not  grow  unless  its  whole 
energies  are  often  directed  towards  a  single  object.  It  is 
not  study  to  read  a  page  and  then  to  converse  about  sports 
for  a  moment  and  then  to  study  another  moment,  for  each 
impression  sweeps  away  the  preceding  one.  True  study 
is  to  sit  down  in  a  quiet  room,  and  to  fix  the  mind  upon  the 
book  continuously  for  an  hour  or  more.  Then  the  mind 
will  be  occupied  so  that  it  takes  no  note  of  time  or  outside 

305 


306  -     APPLIED   PHYSIOLOGY 

impressions.  Any  one  will  find  study  interesting  if  he  will 
concentrate  his  mind  upon  a  subject  so  that  he  gains 
knowledge.  Then  when  playtime  comes  he  will  enter 
into  the  sport  with  zest  and  satisfaction.  No  one  who  has 
not  been  working  can  truly  enjoy  play. 

552.  Persistence  of  mental  impressions.  —  Brain  work  re- 
quires heat  and  energy  like  muscular  work.  The  cells  of  the  cerebrum 
retain  an  impression  of  each  thought,  which  is  deep  and  permanent  in 
proportion  to  the  power  expended  upon  it.  A  lesson  learned  in  a 
minute  makes  some  impression  upon  the  cells,  but  it  is  gone  in  another 
moment.  A  dull  boy  hammers  away  at  a  lesson  by  the  hour,  but  at  the 
end  of  a  year  he  will  have  retained  far  more  than  the  brilliant  boy  who 
loses  his  impressions  as  fast  as  he  gains  them. 

It  is  extremely  difficult  to  efface  impressions  once  really  made  upon 
the  cerebral  cells.  Apparently,  knowledge  may  be  forgotten,  but  some 
day  something  will  cause  the  cells  to  recall  the  impressions.  Thus  it 
is  very  important  to  avoid  all  thoughts  which  we  should  be  ashamed  to 
recall. 

553.  Habit.  — Memories  of  thoughts  often  repeated  may 
arise  in  spite  of  the  will  to  restrain  them,  and  may  compel 
the  motor  region  to  do  acts  which  the  will  utterly  abhors. 
At  first  a  man's  will  has  to  direct  the  thoughts  to  speak 
profane  words.  Soon  the  words  become  so  imprinted  in 
thought  that  they  arise  even  without  his  knowledge. 
Habits  grow  faster  and  stronger  than  the  will  to  overcome 
them.  On  the  other  hand,  one  can  form  a  habit  of  study 
and  of  mind  cultivation  so  that  mental  work  is  a  pleasure. 
The  more  one  works  with  his  mind,  the  more  he  enjoys 
his  work.  The  mind  is  constantly  forming  habits  of 
thought.  Even  if  it  thinks  nothing  bad,  yet  it  may  soon 
acquire  a  lazy  habit  of  not  thinking  at  all. 

554.  Heredity.  —  Impressions  of  any  kind  may  become 
so    permanent   that   one's   children    have   a   tendency   to 


INFLUENCES    WHICH   AFFECT  THE   MIND  307 

acquire  them.  The  son  of  a  criminal  has  a  natural 
tendency  to  become  a  criminal,  and  even  if  he  is  well 
brought  up  in  an  upright  family  he  will  be  far  more  likely 
to  yield  to  temptation  than  a  well-born  child.  Children  of 
educated  parents  take  naturally  to  study.  Children  of 
excitable  and  nervous  parents  will  also  inherit  their 
disposition.  By  education,  natural  tendencies  of  mind  and 
character  can  be  overcome.  If  a  wrong  tendency  is  known 
and  is  not  corrected,  the  blame  for  future  action  of  the 
child  will  lie  with  his  educators  rather  than  with  the  man. 

555.  Unconscious  mind  action.  — When  the  mind  is  intensely 
occupied  it  may  not  take  note  of  severe  sensory  impressions.  Thus 
soldiers  in  battle  often  fight  on,  unconscious  of  severe  wounds.  You 
may  try  in  vain  to  recall  a  name.  Later,  when  you  are  thinking  of 
something  else,  the  name  may  flash  into  your  mind.  You  may  strive 
to  direct  the  mind  to  a  lesson,  but  thoughts  of  a  sick  friend  may  persist 
in  arising,  and  may  shut  out  all  thoughts  connected  with  the  study.  In 
acquiring  any  new  thought  the  mind  must  reason  by  conscious  efforts, 
step  by  step,  until  the  idea  is  clearly  in  view.  Ever  afterward  the  mind 
may  reason  out  the  steps  unconsciously  and  almost  instantly,  so  that  we 
may  lose  sight  of  the  complexity  of  the  mental  processes  involved  in 
forming  the  idea.  Learning  to  perform  any  mental  process  is  essen- 
tially becoming  able  to  do  it  with  little  or  no  conscious  effort.  Then 
the  mind,  relieved  of  the  conscious  direction  of  thoughts  already 
learned,  is  free  to  acquire  new  ones.  Man  is  probably  unconscious 
of  most  of  the  steps  in  his  mental  processes. 

556.  Sleep.  —  It  is  as  impossible  for  the  mind  to  put 
forth  conscious  effort  continually  as  it  is  for  the  mus- 
cles. A  rest  from  conscious  effort  is  called  sleep.  As  a 
rule,  a  man  needs  about  seven  or  eight  hours  of  good 
sleep ;  a  boy  of  sixteen  needs  nine  or  ten  hours,  while  one 
of  six  needs  twelve.  Sleep  should  be  regular,  so  that  the 
brain  may  not  become  excessively  tired  between  times. 
As  a  general  rule,  an  early  hour  both  for  going  to  bed  and 


308  ^  APPLIED    PHYSIOLOGY 

for  rising  is  desirable.  If  a  student  would  go  to  bed  when 
he  feels  sleepy,  and  would  sleep  an  hour  or  two  longer 
each  night,  he  would  feel  able  to  do  more  and  better  work 
during  his  working  hours. 

557.  Sleeplessness.  —  Like  other  organs  while  resting,  the  brain 
contains  but  a  small  quantity  of  blood  during  sleep.  If  a  large  amount 
of  blood  continues  to  flow  through  it,  sleep  will  be  impossible.  Often 
when  a  person  cannot  sleep  he  can  feel  the  pulse  in  his  temples  throb 
and  hear  it  as  his  head  lies  upon  the  pillow. 

A  common  cause  of  sleeplessness  is  an  empty  stomach.  A  light 
lunch  will  often  cause  the  arteries  of  the  abdomen  to  dilate  artd  take  up 
the  blood  which  circulates  in  the  brain  and  so  relieve  the  cause  of  sleep- 
lessness. 

Lack  of  work  during  the  day  may  be  a  cause  of  sleeplessness.  Many 
a  man  finds  himself  suddenly  unable  to  sleep  when  he  retires  from  active 
business.  It  seems  to  be  a  law  of  nature  that  he  who  does  not  work 
cannot  sleep,  for  he  is  not  tired  enough  to  need  a  rest.  Occupation  for 
the  mind  and  body  will  give  such  persons  a  good  night's  sleep. 

Worry  will  also  cause  sleeplessness,  for  it  keeps  the  cells  of  the  brain 
in  action  just  sufficiently  to  attract  the  blood  to  the  head.  The  brain 
can  endure  extremely  hard  work  if  it  only  gets  rest  between  times. 

Narcotics^  like  opium  and  chloral,  will  always  produce  sleep  if  taken 
in  sufficient  doses.  But  they  injure  the  cells  to  a  greater  degree  than 
they  do  good.  In  times  of  anxiety  the  temptation  to  resort  to  them  is 
great,  but  their  use  at  such  times  invariably  leads  to  a  habit  of  using 
them,  with  all  its  accompanying  evils  and  dangers. 

558.  Dreams.  —  Sometimes  during  sleep  the  sensory  and 
motor  regions  recall  their  memories  with  the  vividness  of 
real  life.  This  is  a  drea7n.  The  thought  regions  rarely 
take  part  in  a  dream.  Disordered  memories  of  the  sensory 
and  motor  regions  seem  to  be  realities,  but  in  the  absence  of 
judgment  they  seem  harmonious  and  natural,  and  we  recog- 
nize their  fantastic  nature  only  when  reason  returns  with 
the  waking  hours.  Formerly  dreams  were  supposed  to  be 
heralds  of  events  to  come;  but  now  it  is  known  that  they 
are  but  the  shadows  of  previous  experiences. 


INFLUENCES   WHICH  AFFECT  THE   MIND  309 

559.  Change  of  occupation.  —  When  one  set  of  brain  cells 
has  become  tired,  it  is  well  to  direct  the  thoughts  to  another 
subject  and  let  the  first  set  of  cells  rest.  It  is  a  relief  to 
study  a  history  lesson  after  working  hard  at  arithmetic 
problems.  A  change  of  occupation  is  the  best  kind  of 
rest.  It  is  well  to  alternate  pure  brain  work  with  work 
which,  like  gardening  and  carpentering,  requires  muscular 
effort. 

560.  Healthy  bodies.  —  The  brain  depends  upon  the  blood  and 
digestive  organs  for  the  power  with  which  to  work.  When  any  of  the 
organs  are  acting  improperly  the  brain  is  the  first  to  suffer.  The  strong- 
est brains  are  contained  in  the  healthiest  bodies.  No  kind  of  food  is 
brain  food  more  than  another,  but  fish  and  phosphates  are  hardly  so 
valuable  as  beefsteak  and  salt. 

561.  Exercise  and  brain  work.  — Muscular  exercise  is  needed 
to  keep  the  body  in  the  best  physical  condition.  Thus  it  makes  the 
brain  stronger.  It  also  takes  some  blood  which  otherwise  would  con- 
tinue to  circulate  in  the  brain,  and  thus  it  rests  the  mind  after  work. 

If  exercise  is  continued  until  the  body  is  tired,  no  energy  is  left  for 
the  brain,  but  sleep  comes  on  as  soon  as  the  body  composes  itself  for 
brain  work.  Exercise  for  the  benefit  of  the  brain  should  be  brisk  in 
order  to  produce  the  best  effect  upon  the  circulation  of  the  blood,  but 
it  should  never  be  carried  to  the  point  of  fatigue. 

562.  Nervousness.  —  When  the  brain  is  exhausted  from 
overwork  or  from  worry,  it  has  not  enough  energy  to  con- 
trol itself  or  the  reflex  actions  of  the  spinal  cord.  Slight 
and  strong  sensations  are  equally  unpleasant,  and  the 
effort  to  control  the  feelings  seems  to  increase  the  suffer- 
ing.   Thus  there  arises  a  condition  called  nervousness. 

Nervousness  is  a  lack  of  self-control.  The  judicious  ex- 
pression of  sympathy  by  a  strong-willed  person  is  the  best 
means  of  overcoming  it.  On  the  other  hand,  sarcasm  and 
scolding  only  do  injury  and  increase  the  nervousness. 

563.  Hysteria.  —  An  extreme  lack  of  self-control  is  called 


310  APPLIED   PHYSIOLOGY 

hysteria.  The  person  laughs  or  cries  at  trivial  things.  The 
motor  and  sensory  regions  often  seem  paralyzed.  Persons 
may  even  wound  themselves  to  inspire  sympathy.  Yet 
there  may  be  most  violent  convulsive  movements.  A  well- 
marked  case  closely  resembles  the  actions  of  a  spoiled  child 
when  his  will  is  crossed. 

The  treatment  of  hysteria  is  to  arouse  the  will  power.  Expressions 
of  sympathy  only  make  the  condition  far  worse.  A  firm  and  stern 
nurse  can  usually  command  obedience.  Any  sudden  fright  will  gener- 
ally break  up  an  attack. 

564.  Lisanity.  —  A  persistent  lack  of  control  of  the 
brain  in  one  or  more  directions  is  called  insanity.  Ner- 
vousness often  repeated  and  yielded  to  may  become  insan- 
ity. Worry  and  overwork  are  extremely  common  causes, 
while  alcohol  causes  half  the  cases  in  asylums.  Often  the 
weakness  of  the  brain  cells  is  inherited. 

A  person  about  to  become  insane  is  changed  in  dispo- 
sition and  character.  There  is  a  lack  of  self-control  and 
of  judgment.  Prompt  rest  and  care  of  the  body  may  over- 
come the  attack,  but  a  strong-willed  friend  will  be  needed 
to  guide  the  treatment,  for  the  patient  thinks  that  every- 
body except  himself  is  wrong. 

565.  Forms  of  insanity.  —  In  insanity  there  are  no  new  mental 
traits  or  possessions  by  demons,  as  used  to  be  supposed,  but  only  an  in- 
crease of  some  mental  acts  and  a  decrease  of  others.  The  expression 
an  7inbala7iced  mind  well  describes  the  condition.  There  are  three 
main  forms  of  its  disturbance,  giving  rise  to  three  forms  of  insanity. 

An  increase  or  hastening  of  one  or  all  mental  acts  sometimes  takes 
place.  The  thoughts  flow  faster  than  words  can  express  them,  and  so 
the  talk  is  a  meaningless  gibberish.  The  senses  are  uncommonly  alert, 
and  one  may  think  he  hears  and  sees  things  which  do  not  exist.  He 
cannot  understand  why  others  are  so  slow  and  dull,  and  so  is  apt  to 
show  violent  outbursts  of  temper.     Yet  although  he  may  harm  others, 


INFLUENCES   WHICH  AFFECT  THE   MIND  31 1 

he  will  seldom  hurt  himself  intentionally.  This  condition  is  called 
maniay  and  constitutes  the  popular  idea  of  a  crazy  person. 

In  a  second  form  of  insanity  the  thoughts  flow  slowly.  Questions 
are  answered  in  a  hesitating  way  of  which  the  person  is  conscious,  so 
that  he  feels  that  he  is  incapable  of  doing  business  or  even  associating 
with  men.  He  becomes  gloomy,  and  imagines  he  has  committed  an 
unpardonable  sin  which  he  endeavors  to  discover.  He  reads  his  Bible, 
but  imagines  that  all  its  curses  apply  to  him  personally.  He  finally 
tries  to  destroy  himself  so  that  he  may  no  longer  be  a  burden  to  his 
friends.     This  condition  is  called  inelancholia. 

A  weakening  of  the  whole  brain  is  the  third  form  of  insanity.  De- 
generation of  the  brain  cells  often  occurs  in  old  people,  and  is  commonly 
called  softening  of  the  braiii.  It  may  occur  in  middle  age.  Alcoholic 
drink  is  a  common  cause  of  the  condition. 

566.  Treatment  of  insanity.  —  Insane  persons  can  usually  talk 
and  exercise  some  reasoning  powers.  A  sympathetic  nurse  should  win 
their  confidence  and  control  them  by  reason  and  persuasion.  Special 
training  is  required  to  carry  out  proper  treatment,  and  so  it  is  usually 
best  to  remove  them  to  an  asylum.  Most  cases  of  insanity  improve  in 
from  three  to  six  months,  and  many  permanently  recover. 

567.  Delirium  of  fever.  —  In  poisoning,  either  by  drugs  or  by 
the  poisons  of  sickness,  the  mind  is  apt  to  be  somewhat  disturbed. 
Anything  which  diminishes  the  fever  will  quiet  the  mental  disturbance, 
and  with  the  end  of  the  fever  the  mind  regains  its  right  state.  In  rare 
cases,  the  delirium  persists,  and  is  then  a  real  insanity. 

568.  Injuries  to  the  brain.  —  The  effects  of  a  blow  or 
other  injury  to  the  brain  depend  upon  its  situation.  Any 
injury  may  cause  unconsciousness.  Injuries  to  the  top  of 
the  brain  impair  the  faculties  situated  in  the  injured  regions, 
but  seldom  cause  death.  Injuries  to  the  base  of  the  brain 
are  usually  fatal  by  involving  the  medulla.  After  the  ef- 
fects of  the  blow  have  passed  off,  a  blood  clot  remaining 
may  still  cause  paralysis  of  the  cells  of  a  particular  part  so 
that  the  person  may  lose  certain  mental  powers. 

569.  Apoplexy. — The  arteries  of  old  persons  sometimes 
become  hard  and  brittle  so  that  one  is  liable  to  burst  in  the 


312  APPLIED   PHYSIOLOGY 

brain,  especially  in  its  motor  region.  Then  the  pressure 
of  the  escaped  blood  injures  or  destroys  some  of  the  brain 
cells.  This  constitutes  apoplexy,  or  a  stroke  of  paralysis. 
There  is  usually  unconsciousness  for  a  time,  followed  by 
paralysis  of  some  limb  and  of  speech.  Recovery  is  usually 
slow  and  imperfect.  If  the  medulla  is  affected,  death 
quickly  results.  Confusion  of  speech,  dizziness,  and  tin- 
gling in  a  limb  usually  precede  an  attack  for  some  days. 
When  a  person  is  taken  with  a  stroke  of  apoplexy,  he 
should  be  kept  very  quiet,  with  his  head  raised,  so  that  the 
blood  will  flow  through  the  brain  as  gently  as  possible. 

570.  Fits.  —  If  the  cells  of  the  motor  region  of  the  brain  are  irri- 
tated, as  by  a  sliver  of  bone  or  a  blood  clot,  they  may  send  impulses  at 
intervals  to  produce  violent  movements  of  the  muscles.  This  is  called 
a  convidsioji  or  ayf/.  An  operation  for  the  removal  of  the  substance 
which  presses  upon  the  cells  will  relieve  the  fits. 

In  young  children,  irritation  of  indigestible  food  in  the  intestine  or 
of  the  poisons  of  fevers  may  cause  the  spinal  cord  or  motor  region  to 
send  out  reflex  orders  and  so  produce  a  convulsion  or  fit.  Convulsions 
in  a  child  can  be  stopped  by  immersing  it  in  a  tub  of  very  warm  water. 
Then  something  to  clear  out  its  intestine  should  be  given  so  as  to  re- 
move the  cause  of  the  convulsions.  In  all  forms  of  convulsions  there 
is  little  suffering,  for  the  person  is  wholly  unconscious. 

Convulsions  may  come  without  warning  and  produce  entire  uncon- 
sciousness for  a  minute  or  two,  when  they  cease,  and  the  person  is  ap- 
parently none  the  worse  for  it.     This  trouble  is  called  epilepsy  ox  fits. 

During  the  fit  there  is  no  danger  except  that  a  person  may  bite  his 
tongue.  So  the  only  thing  to  be  done  is  to  stuff  a  handkerchief  into 
his  mouth  so  as  to  crowd  the  tongue  away  from  the  teeth.  Excitement 
is  liable  to  bring  on  fits  in  a  person  subject  to  them. 

571 .  Panics.  —  In  times  of  bodily  or  financial  danger,  where  many 
are  assembled,  a  single  person  may  infect  the  whole  audience  with  an 
insane  fear.  Then  each  person  thinks  only  of  his  own  safety,  and 
many  are  sure  to  be  trampled  upon  and  injured.  In  such  a  time  a 
single  cool  head  will  do  much  to  calm  the  excitement.  Fire  drills  in 
school  teach  the  pupils  to  be  orderly  in  the  face  of  danger. 


INFLUENCES  WHICH  AFFECT  THE  MIND  313 


SUMMARY 

1.  Constant  effort  of  the  will  is  needed  to  keep  the  thought 

cells  of  the  brain  acting. 

2.  A  few  repetitions  of  either  good  or  bad  acts  produce 

Jiabits  of  doing  them. 

3.  Many  mental  acts  are  done  without  consciousness. 

4.  In  sleep  the  thought  cells  rest  from  work  and  there  is 

complete  unconsciousness.  Lack  of  mental  occupa- 
tion during  the  day,  worry,  and  an  empty  stomach 
are  common  causes  of  sleeplessness. 

5.  A  change  of  occupation  is  rest  for  the  mind. 

6.  Active  exercise,  short  of  fatigue,  improves  the  mind 

as  well  as  the  body. 

7.  A  lack  of  self-control  when  irritated  by  slight  sensa- 

tions is  nervousness.  An  extreme  lack  of  will  power 
is  hysteria. 

8.  A    persistent    lack    of    control    of    the    thoughts   is 

insanity.  The  thoughts  may  either  be  hastened,  or 
hindered,  or  suppressed,  giving  rise  to  three  forms 
of  the  trouble. 

9.  In  fevers  there  is  often  a  temporary  delirium  which 

resembles  insanity. 

10.  In  old  people,  an  artery  of  the  brain  sometimes  bursts, 

and  the  clot,  pressing  upon  the  nerve  cells,  stops 
their  action  and  produces  a  shock  of  apoplexy. 

11.  Irritation  of  the  motor  region  may  cause  the  cells  to 

send  orders  for  violent  muscular  movements,  pro- 
ducing a  fit  or  convulsion. 

REVIEW  TOPICS 

I.  State  how  the  cells  of  the  cerebrum  differ  from  the 
other  cells  of  the  body  in  regard  to  being  controlled 
and  made  to  act. 


314  APPLIED   PHYSIOLOGY 

2.  Tell  how  best  to  study. 

3.  Discuss  persistence  of  impressions  ;  habit;  heredity. 

4.  Show  how  the  mind  acts  without  our  knowledge. 

5.  Tell   the    nature    of    sleep;    its   use;    how    much    is 

required ;    and  when  to  sleep. 

6.  Tell    how   sleeplessness    is    produced    by    an    empty 

stomach  ;  by  worry  ;  and  by  lack  of  work. 

7.  Tell  the   nature  of  dreams  and  of  what  ideas  they 

usually  consist. 

8.  Show  how  a  change  of  occupation  rests  the  brain. 

9.  Show  that  good  health  is  needed  for  good  brain  work, 

and  tell  how  exercise  affects  the  brain. 

10.  Show  the  nature  of  nervousness,  and  of  hysteria,  and 

tell  how  to  overcome  them. 

11.  Give  the  causes  of  insanity,  its  three  forms,  and  its 

treatment. 

12.  Give  the  result  of  blows  upon  the  brain. 

13.  Give  the  nature  of   a  stroke  of  apoplexy,  and  show 

how  it  produces  paralysis. 

14.  Discuss  fits  ;  their  causes,  forms,  and  treatment. 

15.  Discuss  panics. 


CHAPTER   XXXIII 

EFFECTS   OF  NARCOTICS   UPON  THE  MIND 

5-72.  Stages  of  action.  —  A  perfect  engine  acts  smoothly, 
and  with  an  ease  of  motion  which  suggests  a  dehght  in  its 
work.  The  body  is  an  engine  at  the  service  of  the  will. 
A  derangement  of  any  part  disturbs  the  action  of  the 
brain  according  to  the  extent  of  the  disorder.  While  little 
or  no  alcohol  can  ever  be  found  in  the  brain,  yet  the  leu- 
comaines  and  other  poisons  produced  by  the  action  of 
alcohol  reach  the  whole  body,  and  produce  a  profound 
effect  upon  the  brain  sooner  than  upon  any  other  part. 
Three  stages  of  the  effects  of  alcohol  are  well  marked :  — 

First,  there  is  a  stage  of  stimulation ;  second,  the  cells 
act  in  an  uncertain  manner.  This  is  the  stage  of  disti^'bed 
action ;  third,  the  cells  act  slowly  or  even  cease  to  act. 
This  is  the  stage  of  paralysis.  All  three  stages  are  often 
seen  in  drunken  men  upon  the  streets. 

573.  Stage  of  stimulation.  —  A  small  amount  of  alcohol 
causes  the  blood  to  circulate  more  rapidly.  More  food 
reaches  the  brain  cells,  and  so  they  show  more  activity. 
It  produces  a  happy  state  of  mind  in  which  men  over- 
estimate their  abilities.  Men  drink  mainly  for  this  effect 
of  the  alcohol. 

Some  gifted  men  with  weak  wills  exert  themselves  only  when  under 
the  influence  of  strong  drink,  and  from  this  fact  many  reason  that 
alcohol  increases  the  brain  power.  These  gifted  men  hang  about  the 
saloons,  eating  little  and  drinking  much.  In  this  condition  their  brains 
receive  no  strength  or  energy  to  devote  to  any  object.     A  drink  fur- 

315 


3l6  APPLIED   PHYSIOLOGY 

nishes  a  quick  stimulation  which  at  once  excites  the  brain  to  great 
activity.  Thus  it  is  enabled  to  do  brilliant  work  while  the  effects  of 
the  alcohol  last.  In  half  an  hour  the  poisonous  effects  assert  them- 
selves, and  the  man's  condition  is  worse  than  ever.  Good  food  and  a 
regular  life  would  give  such  a  man  a  continuous  store  of  energy  with 
which  he  could  perform  brilliant  work  day  after  day.  Alcohol  is  such  a 
poor  substitute  for  the  food  that  it  enables  him  to  work  only  for  a  few 
moments  at  a  time. 

574.  Stage  of  disturbed  action.  —  The  stimulation  of  a 
drink  of  alcohol  is  uncertain,  and,  at  best,  lasts  only  for  a 
few  minutes.  Alcohol  uses  oxygen  which  would  otherwise 
be  available  for  the  brain  cells  as  well  as  for  the  other 
cells  of  the  body.  An  ounce  and  a  half  of  alcohol  a  day 
will  begin  to  interfere  with  oxidation  and  to  disturb  the 
brain,  and  far  less  will  do  so  if  it  all  is  taken  at  once. 

575.  Moral  effect.  —  Alcohol  weakens  and  disturbs  the 
action  of  the  brain  cells,  beginning  with  those  most 
highly  developed.  These  are  thoughts  of  our  relation  to 
other  men.  So  a  person  beginning  to  be  under  the  influ- 
ence of  drink  will  be  selfish  and  inconsiderate  of  others. 
He  will  insult  his  friends  and  get  angry  without  cause. 

576.  Effect  upon  his  judgment. — The  judgment  or 
reasoning  concerning  the  effect  of  one's  acts  upon  himself 
is  the  next  to  be  disturbed.  He  becomes  daring  and 
careless.  He  proposes  impossible  plans  in  business.  If 
he  has  a  tendency  to  commit  a  crime,  he  will  do  it  now. 
Many  a  thief  or  murderer  has  gotten  himself  into  this 
state  of  drunkenness  to  enable  him  to  commit  his  crime 
recklessly.  If  a  man  has  a  tendency  to  swear  or  to  be 
unkind,  he  will  show  it,  for  the  restraint  of  judgment  is 
gone.  The  blunted  judgment  takes  no  note  of  coming 
danger  or  of  business  failure.  Many  a  man  drinks  to 
drown  trouble. 


EFFECTS   OF  NARCOTICS   UPON  THE   MIND  317 

677.  Effect  upon  the  motor  regions.  —  Shortly  after  the 
judgment  is  clouded  the  motor  regions  begin  to  fail.  Then 
the  hand  will  be  unsteady,  and  the  legs  will  totter  as  they 
support  the  body.  The  person  is  now  visibly  drunk,  and 
his  judgment  is  so  far  gone  that  he  could  not  decide  where 
to  go  even  if  his  legs  could  carry  him.  The  cerebellum  is 
also  affected,  so  that  he  is  still  more  uncertain  in  his 
movements. 

578.  Effect  upon  the  sensory  regions.  —  Next  after  the 
motor  regions,  the  sensory  regions  begin  to  fail.  Sensa- 
tions of  touch  are  first  affected,  so  that  the  drinker  cannot 
feel  the  glass  at  his  lips.  In  former  days  it  used  to  be 
the  custom  to  make  a  person  drunk  and  insensitive  before 
he  underwent  a  surgical  operation.  After  the  sensations 
of  touch  are  benumbed  the  sight  begins  to  fail.  A 
drunken  man  sees  double,  or  the  buildings  and  trees  seem 
to  sway  and  dance  before  his  eyes.  Hearing,  smell,  and 
taste  are  also  lessened,  so  that  he  does  not  heed  loathsome 
surroundings,  but  will  lie  contented  in  a  filthy  gutter. 

579.  Stage  of  paralysis.  —  When  the  thought,  motor, 
and  sensory  regions  of  a  man's  brain  are  all  weakened  or 
stopped  in  their  action,  the  mind  is  dull  and  drowsy,  and 
soon  he  is  in  a  condition  resembling  a  deep  sleep,  from 
which  he  can  be  roused  only  with  difficulty.  The  medulla 
and  spinal  cord  still  carry  on  the  processes  of  life,  but 
they  too  begin  to  be  overpowered.  By  the  time  the 
cerebrum  is  almost  overcome,  the  spinal  cord  is  also  much 
decreased  in  action  so  that  there  is  no  response  to  pricks 
or  blows.  Then  the  medulla  is  all  that  remains  of  the 
central  nervous  system.  It  continues  to  send  out  impulses 
for  respiration.  The  respiration  and  circulation  are  the 
only  remaining  signs  of  life,  but  even  they  are  weak, 
and  may  become  almost  imperceptible.     Since  little  oxy- 


3l8  APPLIED   PHYSIOLOGY 

gen  enters  the  body,  little  heat  is  produced.  If  the  night 
is  at  all  cold,  the  drunken  man  is  in  great  danger  of 
freezing  to  death.  It  is  only  a  step  to  the  total  cessation 
of  the  action  of  the  medulla  and  failure  of  respiration. 

In  cities  men  often  are  found  in  the  streets  in  the  last 
stage  of  drunkenness.  They  closely  resemble  cases  in 
which  the  action  of  the  brain  is  destroyed  by  a  severe 
blow  upon  the  head  which  leaves  no  external  mark. 

580.  Effects  of  long-continued  drinking.  —  Either  heavy 
or  moderate  drinking  may  cause  in  the  brain  and  mind 
a  slow  change  which  resembles  an  excessively  slowly 
developed  drunken  state.  As  in  drunkenness,  the  first 
change  is  a  disregard  for  the  comfort  of  others.  Then 
the  thoughts  wander,  and  the  mind  cannot  grasp  a  situa- 
tion as  it  once  could.  Later  the  motor  region  is  affected  so 
that  the  hand  trembles  and  the  gait  is  unsteady.  All  these 
changes  are  like  those  which  naturally  occur  in  old  persons. 
Drink  makes  a  person  old  too  soon.  In  many  drinkers  the 
judgment  entirely  disappears,  and  the  drinker  is  insane. 
He  is  in  a  continual  state  resembling  drunkenness.  Alco- 
hol produces  more  insanity  than  all  other  causes  combined. 

581.  Effects  of  bad  company.  —  The  low  companionship  which 
a  drunkard  keeps,  itself  tends  to  dwarf  the  mind  and  to  make  one  care- 
less in  morals  and  judgment.  Men  also  lead  each  other  into  tempta- 
tion. If  a  man  were  alone,  one  drink  might  satisfy  him,  but  meeting 
others,  he  lingers  to  talk,  and  so  drinks  again  to  keep  company  with 
the  rest. 

582.  Delirium  tremens.  —  After  a  prolonged  drunken  state,  or 
after  severe  injury,  a  heavy  drinker  is  liable  to  violent  disturbance  of 
the  mind,  called  deliriiun  tremens.  In  it  his  sensory  regions  form 
exaggerated  memories  of  fantastic  and  hideous  views,  in  which  demons 
and  foul  reptiles  seem  present  on  purpose  to  torment  him.  In  his  fear 
he  will  cry  out  and  will  use  violence  in  his  endeavors  to  escape.  The 
trouble  may  last  continually  for  several  days,  and  may  permit  the  suf- 
ferer to  take  neither  food  nor  sleep. 


EFFECTS   OF   NARCOTICS   UPON   THE    MIND  319 

583.  Alcoholic  inheritance.  —  The  weak  body  and  mind  of  a 
confirmed  drunkard  are  almost  surely  transmitted  to  his  children,  but  any 
one  who  drinks  at  all  may  transmit  some  undesirable  traits.  The  appe- 
tite for  liquor  also  may  be  transmitted  to  the  children.  If  they  are  kept 
from  temptation,  they  will  lead  temperate  lives,  but  they  will  be  very  apt 
to  yield  to  the  desire  for  drink  if  the  temptation  is  thrown  in  their  way. 

584.  Treatment  of  the  alcoholic  habit.  —  By  a  few  repeti- 
tions of  drink  the  memory  of  it'^  sensations  becomes  so 
strong  that  it  overrules  the  thoughts  and  will,  and  compels 
its  own  gratification  in  more  drink.  At  first,  a  man  can 
resist  the  appeals  of  his  appetite,  but  after  the  cells  of  the 
sensory  region  have  gained  gratification  a  few  times,  they, 
instead  of  the  will,  direct  the  motor  region  to  secure  the 
drink.  Many  a  drunkard  can  no  more  control  his  appetite 
than  he  can  control  the  memory  of  the  drink.  What  was 
once  a  pleasant  memory  of  the  subordinate  sensory  region, 
becomes  the  giant  demon,  enslaving  the  kingly  thought 
regions. 

A  drinker  should  not  be  laughed  at  or  scorned,  but  he 
should  be  encouraged  to  use  his  will  in  overcoming  the 
desire  for  drink.  To  this  end  everything  ennobling  should 
be  placed  in  his  way.  Good  books,  good  companionship, 
and,  above  all,  the  encouragement  of  sincerely  Christian 
people  are  almost  absolute  necessities  in  his  reformation. 

Drugs  have  almost  no  effect  upon  the  habit,  for  they 
cannot  abolish  memory  nor  increase  the  will  power.  Total 
abstinence,  not  only  from  the  drink,  but  also  from  buildings 
where  it  is  sold  and  from  the  association  of  those  who 
have  been  drinkers,  is  necessary  for  a  cure. 

585.  Tobacco.  —  By  smoking,  a  greater  amount  of  blood 
is  drawn  into  the  head,  and  the  increased  flow  of  blood 
seems  to  make  the  brain  more  active.  Sucking  air  through 
a  small  quill  produces  the  same  effect  upon  the  brain  as 


320  APPLIED   PHYSIOLOGY 

sucking  smoke  through  a  pipe.  In  fact,  smokers  often 
cannot  tell  by  the  taste  alone,  whether  the  pipe  or  cigar  is 
alight  or  not ;  but  they  unconsciously  judge  mainly  by  see- 
ing the  smoke.  Since  tobacco  weakens  the  heart,  less 
blood  will  flow  through  the  body  when  tobacco  in  any 
form  is  used,  and  this  fact  will  tend  to  make  the  mind  act 
less  strongly  than  before.  The  nicotine  is  also  a  direct 
nerve  poison. 

586.  Drug  habits.  —  Opium,  cocaine,  and  other  narcotic 
drugs  whose  use  may  become  a  habit,  affect  the  mind  in 
the  same  way  as  alcohol.  Every  one  who  habitually  uses 
any  of  these  drugs  will  surely  become  a  mental  as  well  as 
a  physical  wreck.  Opium,  especially,  seems  to  have  a 
fiendish  effect  in  destroying  the  morality  of  its  users. 
They  begin  by  lying  and  cheating  in  order  to  obtain  the 
drug  without  the  knowledge  of  their  friends,  and  they 
finally  end  by  becoming  dishonest  in  all  things.  But  the 
drug  produces  a  weak  mind  and  body  which  soon  end  in 
death.  Most  of  these  drugs  are  far  more  dangerous  than 
tobacco  or  alcohol. 

587.  Ether  and  chloroform  anaesthesia.  —  Ether  and  chloro- 
form are  both  substances  manufactured  from  alcohol.  When  they  are 
breathed  into  the  lungs  they  produce  effects  which  resemble  a  rapid 
state  of  drunkenness  carried  to  its  last  stao;e.  For  a  brief  time,  the 
brain  is  excited  and  then  its  faculties  disappear  one  after  another.  In 
from  five  to  fifteen  minutes  the  brain  and  spinal  cord  are  completely 
overcome,  and  only  the  medulla  continues  in  action  to  carry  on  respira- 
tion and  the  circulation  of  blood.  A  person  may  be  safely  kept  in  this 
condition  for  two  or  three  hours.  Upon  stopping  the  inhalation  the 
effects  pass  off"  in  reverse  order,  until  in  from  ten  minutes  to  an  hour 
one  has  the  full  use  of  his  brain  again.  The  thought  regions  are  over- 
come long  before  the  motor  regions,  and  so  a  person  taking  ether  may 
struggle  and  cry  out  in  apparent  agony  long  after  he  has  become  com- 
pletely unconscious.  The  struggling  is  reflex  and  takes  place  while  a 
person  is  insensible  to  suffering. 


EFFECTS   OF  NARCOTICS   UPON   THE   MIND  32 1 

SUMMARY 

1.  Because  a  small    quantity  of    alcohol    stimulates  the 

heart  and  increases  the  flow  of  blood  in  the  brain, 
it  stimulates  the  mind  to  greater  action.  This  lasts 
for  a  short  time  only. 

2.  A  little  more  alcohol  is  a  narcotic  to  the  brain  cells 

and  weakens  them  so  that  they  act  in  an  uncertain 
manner. 

3.  The  first  action  to  be  disturbed  is  one's  thoughts  of 

the  welfare  of  others,  and  the  second  is  the  judg- 
ment of  one's  own  affairs.  At  this  stage  the  actions 
are  wild  and  foolish. 

4.  Next  the  motor  region  is  disturbed,  and  a  man  is  now 

noticeably  drunk. 

5.  Next  his  sensory  regions  are  disturbed  so  that  he  can- 

not see  and  hear  and  feel  so  well  as  he  should.  He 
is  now  dull  and  sleepy,  or  dead  drunk. 

6.  Next  the  medulla  is  affected  so  that  the  respiration 

and  action  of  the  heart  are  disturbed.  Then  death 
is  near  at  hand. 

7.  Continued  drinking  slowly  overcomes  the  faculties  of 

the  mind  in  the  same  order  that  they  are  overcome 
in  drunkenness.  When  the  cells  are  seriously 
affected,  the  person  is  insane. 

8.  The  habit  of  taking  alcohol  may  become  so  deeply 

set  in  the  brain  cells  that  it  is  a  disease  overcoming 
the  will. 

9.  Sucking  in  tobacco  smoke  causes  more  blood  to  flow 

to  the  brain,  and  so  slightly  increases  its  power,  but 
the  tobacco  itself  weakens  the  brain. 
10.    Opium,  cocaine,  and  all  other  drugs,  when  habitually 
used,  always  weaken  and  destroy  the  mind. 

OV.  PHYSIOL.  —  21 


322  APPLIED   PHYSIOLOGY 

REVIEW  TOPICS 

1.  Tell  why  alcohol  affects  the  brain  and  give  the  three 

stages  of  its  effects. 

2.  Describe  the  stage  of  stimulation. 

3.  Trace  the  career  of  a  man  as  he  becomes  more  and 

more  under  the  influence  of  drink,  giving  the  effects 
of  alcohol  upon  the  moral  feelings;  upon  the  judg- 
ment ;  upon  the  motor  region  and  cerebellum  ;  upon 
the  sensory  region ;  and  upon  the  medulla. 

4.  Describe  the  permanent  effects  which  long-continued 

drinking  produces  in  the  brain. 

5.  Show  how  the  bad  company  kept  by  drinkers  affects 

their  minds. 

6.  Describe  delirium  tremens. 

7.  Show  that  the  taste  for  alcohol  and  the  effects  of  its 

use  may  be  transmitted  to  children. 

8.  Show  that  the  alcohol  habit  is  a  disease,  and  give  its 

treatment. 

9.  Tell  how  tobacco  affects  the  brain. 

10.  Tell    how    drug   habits,    as   opium    using,   affect   the 

brain. 

11.  Tell  how  ether  and  chloroform  produce  insensibility, 

and  how  the  state  resembles  drunkenness. 


CHAPTER   XXXIV 

TASTE,   SMELL,   AND  HEARING 

588.  Touch.  —  Touch  is  a  special  sense.  Its  sensations 
are  aroused  without  the  need  of  any  special  organ.  So 
the  discussion  of  sensory  nerves  is  really  a  discussion  of 
the  special  sense  of  touch.     (See  p.  269.) 

589.  Taste.  —  Taste  is  a  special  sense  which  is  located 
in  the  tongue,  palate,  and  pharynx.  All  these  parts  are 
endowed  with  a  delicate  sense  of  touch,  but  in  addition 
two  pairs  of  cranial  nerves  carry  special  sensations  of  taste. 
The  impulses  are  aroused  by  the  direct  action  of  sub- 
stances upon  the  nerves.  The  motions  of  chewing  and  a 
good  flow  of  saliva  aid  the  sense  of  taste  by  bringing  food 
in  contact  with  the  nerves,  while  a  dry  substance,  or  one 
which  will  not  dissolve  in  water,  can  have  no  taste.  All 
tastes  are  some  combination  of  sweet,  sour,  bitter,  and  salt 
tastes.  Sweetness  and  sourness  are  recognized  mainly  by 
the  front  part  of  the  tongue,  and  bitterness  and  saltness 
by  the  back  parts  and  pharynx. 

Taste  is  greatly  influenced  by  the  sense  of  smell.  The 
real  taste  of  coffee  is  greatly  changed  by  the  odor  which 
reaches  the  back  part  of  the  nose  as  it  is  swallowed. 

590.  Use  of  taste.  —  Taste  enables  a  man  to  detect 
spoiled  or  unwholesome  food.  The  sense  is  capable  of 
great  education.  The  prices  of  different  grades  of  tea  are 
determined  by  expert  tea  tasters,  who  devote  their  whole 
time  to  tasting  different  samples.      Alcohol  and  tobacco 

323 


324 


APPLIED   PHYSIOLOGY 


irritate  the  nerves  in  the  mouth  and  so  blunt  the  taste  for 
good  food.  For  this  reason  a  drinker  does  not  enjoy  plain 
food,  but  requires  spices  to  excite  his  taste. 

591.    The  nose.  —  Impressions  of  smell  originate  within 
the  nose.      Each  nostril  leads  to  a  wedge-shaped  cavity, 


The  outer  wall  of  the  nose. 


a  the  nerve  of  smell  at  the  base  of  the 

brain. 
l>  air  spaces  in  the  skull  bones. 
c  branches  of  the  nerve  of  smell. 


d  curved  curtains  of  bone. 

e  opening  of  the  Eustachian  tube. 

/  soft  palate. 

^  upper  jawbone. 


which  opens  into  the  pharynx.  The  inner  wall  of  each 
cavity  is  smooth,  and  is  formed  by  the  thin  bone  that 
separates  the  two  nostrils.  Each  outer  wall  is  formed  by 
three  very  thin  bones  which  hang  down  like  narrow  cur- 
tains. They  nearly  cover  cavities,  called  simises,  which 
are  situated  in  the  neighboring  bones.  One  sinus  occupies 
the  interior  of  the  upper  jawbone,  and  is  called  the  antrum. 
The  part  of  the  skull  behind  the  eyebrows  is  honeycombed 
with  small  cavities,  called  \\\q  frontal  sinuses. 


TASTE,   SMELL,   AND    HEARING  325 

592.  Olfactory  nerves.  —  From  the  under  surface  of  the 
brain,  about  twenty  nerves  extend  through  perforations  in 
the  upper  part  of  the  nose  and  spread  out  over  the  upper 
one  third  of  the  surface  of  the  nasal  cavities.  An  odorous 
gas  entering  the  nose  comes  in  contact  with  the  ends  of 
these  nerves  and  excites  the  sense  of  smell.  An  odor  is 
found  only  in  substances  which  can  be  turned  to  a  vapor. 

The  olfactory  nerves  are  so  delicate  that  they  can  perceive  the 
presence  of  gases  which  cannot  be  detected  in  any  other  way.  Some 
substances  excite  the  sense  of  smell  when  they  are  in  such  small  quan- 
tities that  they  are  given  off  for  years  without  causing  a  perceptible 
lessening  of  the  weight  of  the  substance. 

When  too  much  mucus  covers  the  nerve  endings,  or  when  the  sur- 
face of  epithelium  is  dry,  no  gas  can  reach  the  nerves,  and  then  the 
sense  of  smell  is  diminished.  A  cold  in  the  head  can  produce  either 
condition. 

593.  Use  of  smell.  —  Smell  is  a  warning  against  foul  air 
and  decaying  matter.  The  gases  themselves  are  in  too 
small  quantities  to  do  harm,  yet  they  are  a  sign  that 
other  substances  are  present  which  can  harm  the  body. 
Air  which  has  no  odor  is  almost  surely  fit  to  be  breathed. 
Meat  which  has  a  pleasant  odor  is  almost  certainly  fresh. 

Tobacco  smoke  and  snuff  are  irritating  to  the  delicate 
nerves  of  smell,  and  partly  deprive  its  users  of  nature's 
most  useful  protection  against  foul  air. 

594.  The  inner  ear.  —  Sound  is  produced  by  certain  air 
waves  which  are  received  by  nerves  in  the  ear.  There 
they  excite  impulses  which  the  brain  interprets  as  sound. 
In  the  hard  bone,  which  rises  from  the  bottom  of  the 
skull  by  each  ear,  is  a  tortuous  cavity,  called  the  laby- 
rinth or  internal  ear.  The  center  of  the  labyrinth  is  about 
one  eighth  of  an  inch  in  diameter,  and  is  called  the  ves- 
tibule.    From  the  vestibule  there  extends  a  small  spiral 


326 


APPLIED   PHYSIOLOGY 


tunnel,  called  the  cochlea,  which  is  like  the  inside  of  a 
snail's  shell,  and  also  three  other  tunnels  called  the  semi- 
circular cajialsy  from  their  shape. 

The  labyrinth  is  filled  with  a  clear  liquid,  and  is  lined 
with  epithelial  cells,  among  which  the  nerves  of  hearing 
end.  Upon  the  surface  of  the  epithelium  are  cilia,  among 
which  are  fine  hard  particles  called  the  ear  sand.  The  air 
waves  produce  waves  in  the  liquid  which  beat  against  the 


Diagram  of  the  ear. 

outer  air  passage.  /  semicircular  canals. 

membrana  tympani.  g  vestibule  of  inner  ear. 

malleus  or  hammer  bone.  h   cochlea, 

incus  or  anvil  bone.  i    Eustachian  tube. 

stapes  or  stirrup  bone.  J    tympanum  or  middle  ear. 


cilia  and  produce  the  sense  of  sound.  Waves  in  the  fluid 
surrounding  the  nerves  must  occur  at  least  sixteen  times  a 
second  in  order  to  produce  a  sound.  When  they  occur 
more  than  thirty-eight  thousand  times  a  second,  they  are 
too  rapid  for  the  nerves  to  take  account  of  their  motion, 
and  so  no  sound  at  all  will  be  heard. 

The  semicircular  canals  do  not  seem  to  be  essential  to  hearing,  but 
when  they  are  diseased  a  person  is  unable  to  balance  himself  so  as  to 
walk  or  even  to  stand.  The  movements  of  the  fluid  in  the  canal  seem 
to  produce  nervous  impressions  which,  in  the  cerebellum,  excite  such 
reflex  actions  as  are  necessary  to  balance  the  body  in  an  upright  position. 


TASTE,   SMELL,   AND   HEARING  327 

595.  The  middle  ear.  —  To  make  hearing  distinct,  a 
special  mechanism  is  provided  for  transmitting  the  air 
vibrations  to  the  inner  ear  through  two  outer  cavities. 

A  small  aperture  connects  the  inner  ear  with  a  middle 
cavity  called  the  middle  ear,  or  tympanum.  The  middle 
ear  is  half  an  inch  long  and  a  quarter  of  an  inch  broad. 
It  is  lined  with  mucous  membrane  and  is  filled  with  air.  Its 
outer icnd  is  closed  like  a  drum,  by  a  thin  leaf  called  the 
drum  membrane  or  mernbrana  tympani,  while  a  similar  mem- 
brane closes  the  aperture  to  the  inner  ear.  The  cavity  of 
the  middle  ear  is  greatly  increased  by  its  extending  back- 
ward into  a  bony  projection  called  the  mastoid  process, 
which  can  be  felt  just  behind  the  outer  ear.  It  connects 
with  the  pharynx  by  means  of  a  tube  which  is  about  the 
size  of  a  knitting  needle  and  is  called  the  Eustachian 
tube.     The  act  of  swallowing  opens  the  tube. 

596.  Bones  of  the  middle  ear.  —  The  essential  part  of  the 
middle  ear  is  a  chain  of  small  bones  called  the  malleus^ 
incus,  and  stapes,  which  extend  across  its  cavity  from  one 
membrane  to  the  other. 

Air  waves,  striking  the  ear  drum,  throw  it  into  vibra- 
tions, which  the  chain  of  bones  transmits  to  the  inner  ear. 
The  tympanum  and  its  extension  into  the  mastoid  cells 
act  like  the  sounding  box  of  a  violin  to  increase  the 
vibrations. 

597.  Deafness.  —  The  Eustachian  tube  permits  air  to  pass  in  and 
out  of  the  middle  ear  so  as  to  keep  the  air  pressure  within  the  same  as 
it  is  outside.  When  it  is  closed,  the  air  pressure  outside  may  change, 
and  thus  the  drum  membrane  will  be  pressed  upon  and  prevented  from 
vibrating  freely.  This  results  in  partial  deafness.  Enlarged  tonsils 
and  adenoid  vegetations  are  liable  to  cause  a  stoppage  of  the  tube  and 
to  produce  deafness,  and  for  this  reason  they  should  always  be  removed. 
When  the  tube  is  stopped,  there  is  a  feeling  of  fullness  in  the  ear,  and 
roaring  or  singing  noises  will  be  heard. 


328  APPLIED   PHYSIOLOGY 

Deafness  due  to  a  stoppage  of  the  Eustachian  tube  is  the  most  com- 
mon form.  It  often  can  be  reUeved  by  opening  the  tube  by  swallow- 
ing. By  blowing  the  nose  hard  with  the  nose  and  mouth  closed  and  at 
the  same  time  puffing  out  the  cheeks  and  swallowing,  one  can  almost 
always  force  air  through  the  tube  into  the  ear  and  thus  relieve  the  deaf- 
ness.    This  should  be  done  several  times  a  day. 

Sometimes  an  inflammation  extends  from  the  pharynx  up  the  Eusta- 
chian tube  and  sets  up  an  inflammation  in  the  middle  ear  like  that  in 
the  throat.  Mucus  and  matter  then  collect  in  the  middle  ^ar  and 
press  upon  the  ear  drum,  causing  a  severe  earache.  If  the  tube  does 
not  open,  the  membrane  may  burst  and  allow  the  matter  to  run  out  of 
the  ear. 

598.  A  rumiing  ear  should  be  kept  clean  by  cleansing  it  with  warm 
boiled  water  as  often  as  the  matter  collects.  Sometimes  in  running  ears, 
the  disease  eats  away  the  bones  and  produces  inflammation  of  the  brain. 
For  this  reason  running  ears  are  always  dangerous. 

Some  drugs  may  produce  a  ringing  in  the  ears  and  partial  deafness. 
Quinine,  which  is  taken  for  malaria,  and  salicylic  acid,  which  is  taken  for 
rheumatism,  may  cause  it,  but  the  effects  pass  off"  within  a  few  hours. 

Boxing  the  ears  suddenly  compresses  air  against  the  drum  mem- 
brane, producing  pain  and  sometimes  even  bursting  the  membrane. 
Loud  reports,  as  of  cannon,  cause  such  extensive  and  painful  vibra- 
tions of  the  membrane  that  deafness  may  result. 

599.  Early  in  life  a  child  may  become  deaf,  and  yet  no 
one  may  be  aware  of  the  trouble.  Then  the  child  is  appar- 
ently inattentive  and  does  not  answer  when  spoken  to. 
At  school  the  teacher  may  ascribe  his  lack  of  attention  to 
carelessness  or  ill  temper.  In  consequence,  the  child  re- 
ceives unjust  punishment.  The  hearing  of  every  dull  and 
inattentive  child  should  be  examined. 

600.  The  outer  ear.  —  Outside  of  the  drum  membrane 
is  a  passage  to  the  air  about  an  inch  in  length  and  one 
quarter  of  an  inch  in  diameter,  formed  partly  of  bone  and 
partly  of  flesh.  Around  its  opening  is  a  shell-shaped  fold 
of  flesh  which,  together  with  the  passage,  is  called  the 
outer  ear.       Connected   with  it  arc    rudimentary  muscles 


TASTE,   SMELL,   AND    HEARING  329 

which  are  so  well  developed  in  some  persons  that  they  can 
move  their  ears  as  a  horse  does. 

601.  Ear  wax.  —  The  epithelium  of  the  outer  half  of  the 
passage  secretes  a  kind  of  bitter  and  sticky  wax  which 
keeps  insects  and  dust  from  reaching  the  drum  mem- 
brane. The  epithelium  grows  outward  towards  the  surface 
like  the  nails,  and  carries  the  wax  with  it,  thus  preventing 
its  accumulation.  Often  in  picking  the  ears  the  wax  is 
pushed  against  the  drum  membrane  so  that  it  cannot 
vibrate.  Next  to  throat  trouble  this  is  the  most  common 
cause  of  deafness.  The  accumulated  wax  can  be  softened 
and  removed  by  gently  syringing  with  warm  water.  Wax 
can  best  be  removed  with  the  loop  of  the  smallest-sized 
hair  pin,  taking  care  not  to  insert  it  far  enough  to  touch 
the  drum  membrane. 

602.  Illusions  of  hearing.  —  Too  dense  or  too  rare  air  in 
the  middle  ear,  too  much  blood  circulating  in  the  inner  ear, 
the  use  of  certain  drugs,  as  quinine,  blows  upon  the  head 
or  wax  in  the  ear,  are  all  causes  which  may  excite  the 
nerves  of  hearing.  Then  the  impression  goes  to  the 
brain  as  though  a  real  sound  had  excited  the  nerves. 

The  cells  of  the  brain  itself  may  interpret  a  sensation 
wrongly  ;  thus  an  insane  person  may  think  that  the  sound 
of  his  own  pulse  beating  in  his  ears  is  the  echo  of  the 
blows  of  demons  within  his  head. 

Sometimes  persons  recall  memories  of  sounds  so  vividly 
that  they  seem  to  be  real.  This  occurs  naturally  in  dreams, 
but  it  may  occur  in  an  insane  person  at  any  time. 

603.  The  ear  in  lower  animals.  —  In  four-footed  animals 
and  in  birds  the  ear  is  the  same  as  in  man.  In  turtles  and 
frogs  there  is  no  outer  ear,  but  the  drumhead  lies  just 
under  the  skin,  forming  a  visible  circle  behind  the  eyes, 
while  the  middle  ear  contains  a  single  bone.     In  the  snake 


330  APPLIED   PHYSIOLOGY 

there  is  no  external  or  middle  ear,  although  a  bone  extends 
from  the  inner  ear  to  a  kind  of  drum  membrane  just  under 
the  skin.  In  the  fish  there  is  no  external  or  middle  ear, 
and  the  labyrinth  has  no  cochlea,  but  the  vibrations  are 
transmitted  only  through  the  skull.  In  the  lobster  there  is 
a  small  cavity  filled  with  liquid,  in  which  are  the  endings 
of  the  nerves  of  hearing.  The  vibrations  producing  sound 
are  transmitted  to  the  bag  through  the  sides  of  its  head. 
Thus  all  animals  which  have  ears  at  all,  possess  what  in 
man  is  the  internal  ear. 


SUMMARY 

1.  The   sense   of    taste   is   excited   by  substances  which 

become    dissolved    in   the  saliva   and  excite  special 
nerves  in  the  tongue  and  pharynx. 

2.  The  sense  of   taste    enables  one    to    distinguish  good 

food  from  bad. 

3.  The  sense  of   smell  is  excited   by  minute  amounts  of 

gas,  which  excite  special  nerves  in  the  upper   part 
of  the  nose. 

4.  Smell   guards   us   against  foul    air   and    decayed    sub- 

stances. 

5.  Sound  is  produced  by  vibrations  of  the  air. 

6.  The    inner   ear  consists  of   winding  capals  filled  with 

liquid    into    which    special    nerves    project.      Vibra- 
tions of  the  air  excite  the  nerves  and  produce  the 

sense  of  sound. 

7.  The  middle  ear  consists  of  a  bony  cavity  across  which 

three  small  bones  convey  the  vibrations  of  the  air 
to  the  inner  ear. 

8.  Deafness  is  often  caused  by  the  Eustachian  tube  being 

stopped. 


TASTE,   SMELL,  AND   HEARING  33 1 

9.    Inflammation  of  the  throat  may  extend  into  the  middle 
ear  and  produce  an  earache. 

10.  Enlarged  tonsils  and  adenoid  vegetations  are  the  two 

principal  causes  of  earache  and  deafness. 

11.  Running  ears  should  be  kept  clean. 

12.  In  all  animals  having  a  hearing  apparatus,  the  essen- 

tial and  often  the  only  part  is  the  inner  ear. 

DEMONSTRATIONS 

130.  Examine  the  tongue  of  one  of  the  pupils.  Notice  that  its  sur- 
face contains  three  kinds  of  projections.  There  is  a  V-shaped  row  of 
large,  flat,  and  smooth  projections  upon  its  back  part.  There  are  red 
pinhead-sized  projections  scattered  over  the  whole  front  surface.  There 
are  also  fine  projections  like  velvet  spread  over  the  whole  surface.  In 
all  these  projections  the  nerves  of  taste  seem  to  end.  Examine  also  a 
cat's  tongue,  and  note  the  stiff  hairs  upon  its  surface. 

131.  Test  the  power  of  taste  in  different  parts  of  the  tongue.  Place 
a  bit  of  a  sweet  or  of  a  sour  substance  in  the  back  of  the  mouth,  and  notice 
the  slight  taste,  while  it  is  easily  tasted  in  the  front  part.  Now  place 
some  salt  or  bitter  substance  upon  the  front  of  the  tongue.  Notice  that 
it  has  little  taste  until  it  spreads  to  the  back  part. 

132.  Saw  lengthwise  through  a  calf's  head  so  as  to  open  the  nose. 
Notice  the  smooth  inner  surfaces  of  the  nostrils,  and  their  furrowed 
outer  surfaces  produced  by  the  folded  bones.  Notice  that  the  nostrils 
open  into  the  pharj-nx.      (See  demonstration  35.) 

133.  Have  a  butcher  remove  the  bone  containing  the  middle  and 
internal  ear  from  a  calf's  skull.  Carefull}-  cut  away  the  shell  of  bone 
over  the  middle  ear.  One  can  judge  of  its  position  by  measuring  down 
the  outer  air  passage.  Notice  the  size  and  shape  of  the  middle  ear. 
Notice  the  ear  drum,  and  the  three  little  bones  which  stretch  from  it 
entirely  across  the  cavity.  Notice  also  that  the  last  bone  fits  into  the 
small  opening  leading  into  the  inner  ear. 

134.  The  inner  ear  will  be  more  difficult  to  show,  for  it  is  small  and 
complicated,  and  is  situated  deep  in  a  very  hard  bone.  Cut  away  the 
bone  a  little  farther  in,  when  the  cochlea  may  be  opened,  and  possibly 
a  semicircular  canal  will  be  recognized.  The  spiral  tube  of  the  cochlea 
is  barely  5  of  an  inch  in  diameter,  while  the  semicircular  canals  are  as 
small  as  a  sewing  needle,  but  yet  form  loops  about  f  of  an  inch  across. 


332  APPLIED   PHYSIOLOGY 

REVIEW  TOPICS 

1.  Describe  the  process  of  tasting,  and  tell  how  smell 

influences  the  sense  of  taste. 

2.  Give  the  use  of  the  sense  of  taste. 

3.  Describe  the  endings  of   the  nerves  of  smell  in  the 

nose,  and  tell  how  the   sensation   of   smell  is  pro- 
duced. 

4.  Give  the  use  of  the  sense  of  smell. 

5.  Describe    the    inner    ear  :    its    cochlea,    semicircular 

canals,  and  nerves  of  hearing,  and  tell  how  they  act. 

6.  Describe   the  middle  ear :    its  bones,   the  two  mem- 

branes which  close  it,  and  its  Eustachian  tube. 

7.  Show  how  a  stoppage  of   the  Eustachian  tube  may 

lead  to  deafness  ;  to  running  ears. 

8.  Show  how  throat  trouble  may  cause  ear  disease. 

9.  Tell  how  to  care  for  running  ears. 

10.  Show  why  boxing  the  ears  is  dangerous. 

1 1.  Describe  the  outer  ear  :  its  air  passage  and  wax. 

12.  Show  how  the  ears  may  seem  to  hear  sounds  which 

do  not  exist. 

13.  Describe  the  ear  in  a  frog ;  in  a  snake ;  in  a  fish ;  in  a 

lobster. 


CHAPTER   XXXV 


THE   EYE 


604.  Light.  —  Straight  lines  of  light  called  rays  pass  off 
from  objects  in  ail  directions.  Each  ray  is  supposed  to  be 
a  vibrating  line  in  a  thin 
substance  called  ether, 
which  fills  all  space. 

The  vibrations  of  ether  take 
place  many  millions  of  times 
each  second.  In  sound  the  air 
vibrates  only  a  few  hundred 
times.  Light  travels  nearly 
185,000  miles  each  second,  while 
sound  travels  about  1000  feet  in 
the  same  time.  Light  waves  are 
from  30^^  to  60^00  inch  in 
length,  but  each  sound  wave 
reaches  several  feet.  The  length 
of  a  wave  of  light  determines  its 
color.  Red  waves  are  about 
twice  as  long  as  violet  waves. 
A  mixture  of  all  colors  produces 
white  light,  while  black  is  due 
to  the  absence  of  light.  Colors 
which,  like  red  and  green,  form  white  light,  are  called  complementary 
colors. 

In  passing  through  glass  or  other  clear  substances,  rays  of  .light  may 
be  bent  from  their  courses.  By  a  properly  shaped  glass  called  a  lens, 
rays  may  be  spread  apart  or  may  be  brought  together  in  a  point  called 

33Z 


Diagram  of  light  passing  from  an  object. 

It  passes  in  every  direction,  and,  falling 
upon  a  screen,  produces  a  confused  multi- 
tude of  images,  which  form  only  a  mass  of 
light,  but  no  one  clear  image. 


334 


APPLIED    PHYSIOLOGY 


2i  focus.     If  the  focus  falls  upon  a  screen,  an  image  of  the  object  giving 
the  light  will  appear.     By  changing  the  kind  and  the  position  of  the 

lens  the  image  may  be 
made  either  larger  or 
smaller  than  the  real 
object. 

Light  has  the  power  to 
produce  a  chemical  change 
in  substances.  Photog- 
raphy and  bleaching 
clothes  are  examples  of 
the  action  of  light.  In 
photography    a    prepared 


Diagram  of  the  formation  of  an  image  with  a 
lens. 


a   an  object  sending  off  light. 

b  a  lens  which  brings  all  the  rays  from  any  point  plate  is  inclosed  in  a  tight 
in  the  object  together  again  into  a  single  black  box,  into  which  light 
point.  '  ° 

c    image  of  the  object  a.  fi'O"^  an  object  is  admitted 

through     a     small     lens. 

The   lens   brings  the    light  to  a  focus  and  forms  an  image  upon  the 

plate. 

605.  The  eye.  —  The  eye  is  an  apparatus  like  a  photog- 
rapher's camera,  but  is  more  perfect.  It  consists  of  a 
round,  hollow  shell  about  -|  of  an  inch  in  diameter,  formed 
of  a  very  tough  membrane  about  ^  of  an  inch  in  thick- 
ness, called  the  sclerotic  coat.  The  sclerotic  coat  is  lined 
with  a  thin  black  membrane  called  the  choroid  coat,  which 
carries  the  blood  tubes,  and  is  colored  black  so  as  to 
prevent  reflection  of  the  rays  of  light.  Inside  of  the 
choroid  coat  is  a  very  thin  and  transparent  membrane 
called  the  retina.  The  cavity  of  the  eyeball  is  filled 
in  front  with  a  thin,  clear  liquid  called  the  aqueous  Immor, 
while  its  back  part  contains  a  thick,  jellylike  fluid  called 
the  vitreous  humor.  The  two  humors  keep  the  eyeball 
distended  and  in  shape. 

The  nerve  of  sight,  called  the  optic  nerve,  enters  the 
back  part  of  the  eye  and  separates  into  fine  threads  which 
end  in  microscopic  rods  set  closely  together  on  their  ends 


THE   EYE 


335 


in  the  retina.  The  retina  corresponds  to  the  photographic 
plate  of  a  camera.  A  bulging  transparent  tissue,  called 
the  cornea^  forms  a  round  window  through  the  front  part 
of  the  eyeball,  and  admits  light  to  the  retina.  Behind  the 
cornea  is  hung  a  curtain  called  the  iris,  in  whose  center  is 
a  hole  called  the  pupil.     The  iris  is  colored  to  a  shade 


a  bone  of  the  orbit. 

b    muscle  which   moves 

the  eyeball. 
c   sclerotic  coat. 
d  choroid  coat. 


The  human  eye. 

e    retina. 
f  eyelid. 
g  iris. 
h  lens. 


cornea. 

muscle  which  changes 

the    shape   of   the 

lens, 
optic  nerve. 


varying  from  blue  to  dark  brown,  and  it  is  this  which  gives 
the  color  to  the  eye. 

The  iris  is  composed  of  muscle  fibers  which  can  contract  so  as  to 
make  the  pupil  smaller.  A  strong  light  acts  in  a  reflex  way  to  cause 
the  iris  to  contract  and  make  the  opening  of  the  pupil  smaller,  but  in  a 
dim  light  the  pupil  is  large,  so  as  to  admit  all  the  light  possible.  Thus 
the  iris  regulates  the  amount  of  light  admitted  to  the  retina. 

606.  Sight.  —  Behind  the  pupil  is  a  lens  whose  shape 
can  be  changed  at  will  by  the  action  of  muscles.     The 


336  APPLIED   PHYSIOLOGY 

lens  brings  the  light  to  a  focus  so  as  to  form  an  image  of 
an  object  upon  the  retina.  In  the  cells  of  the  retina  are 
particles  of  brown  coloring  matter  in  which  light  produces 
an  instant  change.  This  excites  in  the  optic  nerve  an 
impulse  which  the  brain  interprets  as  sight. 

607.  Coverings  of  the  eye.  —  The  eyeball  is  loosely  situ- 
ated in  a  deep  depression  of  the  skull,  called  the  orbit. 
The  space  between  it  and  the  bone  is  padded  with  fat  and 
crossed  by  numerous  muscles,  nerves,  and  blood  tubes. 
Thus  it  is  thoroughly  protected  from  injury.  It  can  be 
freely  turned  at  will  in  all  directions  by  six  slender  mus- 
cles which  rise  from  the  back  part  of  the  orbit.  It  is  pro- 
tected in  front  by  two  thin  but  strong  lids,  which  can  be 
moved  up  and  down  at  will.  From  the  edges  of  the  lids 
there  project  two  or  three  rows  of  stiff  curved  hairs,  which 
still  further  protect  the  eye.  The  lids  can  be  closed  by  a 
flat  circular  muscle  which  completely  surrounds  them. 
The  insides  of  the  lids  and  the  front  side  of  the  eyeball, 
except  the  cornea,  are  covered  with  a  soft  mucous  mem- 
brane, called  the  conjunctiva. 

608.  Tears. — The  conjunctiva  and  cornea  are  mois- 
tened by  a  saltish  fluid  called  tears.  Tears  are  secreted  by 
a  gland  called  the  lac Jirymal  ^diVi^,  which  is  situated  just 
above  and  to  the  outer  side  of  the  eyeball.  At  the  inner 
end  of  the  edge  of  each  lid  is  the  opening  of  a  small  tube 
which  unites  with  the  tube  from  the  other  lid  and  forms  a 
single  tube  called  the  nasal  duct,  leading  to  the  nose. 
Ordinarily  the  nasal  duct  drains  away  the  tears  as  fast 
as  they  are  formed,  and  sometimes,  as  in  crying,  their 
salt  taste  can  be  noticed  in  the  mouth.  Often  they  are 
produced  so  fast  that  some  run  over  the  lids  and  fall  down 
the  face.  The  uses  of  tears  are  to  wash  away  particles  of 
dust  which  fall  upon  the  eyeball,  and  to  moisten  its  surface. 


THE   EYE  337 

609.  Field  of  view.  —  A  person  can  clearly  recognize 
objects  in  only  a  small  part  of  the  field  of  view  just  in 
front  of  the  eyes,  while  the  rest  seems  to  be  only  indistinct 
shadows.  To  be  distinct,  the  image  must  fall  upon  the 
part  of  the  retina  less  than  ^  of  an  inch  across,  which  is 
situated  directly  behind  the  cornea.  In  reading  a  book, 
the  eye  can  distinctly  see  two  or  three  words  at  once,  but 
by  rapid  and  unconscious  movements  of  the  eyes  sidewise, 
we  cover  a  larger  field  of  view. 

610.  Duration  of  sensations.  —  The  sensation  of  sight  is 
produced  almost  instantly  when  the  eyes  are  directed 
towards  an  object,  but  the  image  persists  for  -^-^  of  a 
second.  If  a  succession  of  pictures  of  a  moving  object 
are  thrown  upon  a  screen  at  that  rate,  the  object  will  seem 
to  go  through  its  motions  without  interruption.  Birds 
flying  and  waves  dashing  upon  the  beach  may  be  thus 
shown  absolutely  true  to  life.  A  point  of  light  swung 
about  a  circle  seems  to  be  a  shining  ring.  If  two  colors 
are  revolved  at  that  rate,  the  eye  no  longer  sees  either  one, 
but  a  mixture  of  the  two.  Thus  a  blue  and  a  yellow  spot 
side  by  side,  when  revolved  before  the  eye,  seem  a  single 
green  spot. 

611.  Color  blindness.  —  Sometimes  the  nerves  of  the 
retina  are  unable  to  recognize  certain  colors.  In  the 
most  usual  form  of  color  blindness  red  is  supposed  to 
be  green  or  gray.  In  locomotive  engineers  and  sailors 
color  blindness  may  be  a  serious  defect,  for  they  are 
guided  by  different  colored  signals,  especially  those  con- 
taining red. 

612.  Exhaustion  of  the  retina.  —  When  the  eyes  look 
steadily  at  objects  for  a  long  time  the  vision  becomes 
blurred.  If  one  gazes  steadily  at  a  bright  colored  object, 
the  retina  is  fatigued  by  that  color.    A  white  object  looked 

OV.  PHYSIOL. —  22 


338  APPLIED   PHYSIOLOGY 

at  now  will  show  a  colored  spot  shaped  like  the  first  object, 
for  a  part  of  the  retina  is  no  longer  able  to  recognize  all 
the  colors  which  make  white  light.  Its  color  will  always 
be  complementary  to  the  color  of  the  object  first  looked  at. 
Thus  when  a  red  object  is  used  first,  a  green  image  ap- 
pears. The  eye  is  really  made  color  blind  for  a  brief 
period. 

Ordinary  lamps  and  gas  jets  give  a  yellowish  light,  while  the  sunlight 
is  white.  So  by  lamp  light,  the  colors  of  objects  seem  to  be  changed. 
In  incandescent  electric  lamps  the  light  is  given  ofif  from  a  white-hot 
filament.  Owing  to  its  steadiness,  its  color  and  the  absence  of  heat 
and  foul  gases,  it  is  the  most  agreeable  light  in  common  use. 

613.  Care  of  the  eyes.  —  No  light  should  be  strong  enough  to 
dazzle  the  eyes.  When,  as  in  public  halls,  bright  lights  are  in  front  of 
the  eyes,  there  is  a  natural  tendency  to  gaze  directly  at  them,  thereby 
tiring  the  retina.  It  would  be  better  to  look  at  the  darkest  objects  in 
the  room. 

It  is  best  to  have  the  light  come  from  behind  the  eye.  In  working 
with  a  lamp  in  front  of  the  eyes,  a  shade  should  cover  either  the  light 
or  the  eyes.  When  the  sun  shines  brightly  upon  the  snow  the  excess 
of  light  exhausts  the  retina.  Then  the  eyes  become  painful,  and  blind- 
ness may  result. 

614.  Contraction  of  the  pupil.  —  A  strong  light  excites 
the  reflex  center  in  the  optic  tubercles  to  send  out  an 
order  for  the  contraction  of  the  muscles  of  the  iris  so  as 
to  make  the  pupil  smaller.  On  the  other  hand,  in  the 
dark  the  pupil  is  large,  so  as  to  admit  all  the  light  possi- 
ble. When  a  light  is  very  strong,  the  reflex  centers  send 
orders  to  the  muscles  both  of  the  upper  and  lower  lids, 
and  of  the  eyebrows  to  pucker  themselves  over  the  eyes, 
so  as  to  leave  only  a  narrow  slit  for  the  entrance  of  light. 
In  this  way  the  eyes  are  well  protected  against  too  strong 
lights,  but  the  contracted  muscles  may  become  tired  and 
painful. 


THE   EYE  339 

615.  Accommodation.  —  Rays  of  light  coming  from  a  dis- 
tant object  are  less  diverging  than  when  coming  from  one 
near  by  ;  then  the  lens  does  not  need  to  bend  them  so  much 
as  in  seeing  objects  near  by.  Adjusting  the  lens  of  the 
eye  to  near  or  far  vision  is  called  accommodation.  When 
the  eye  muscles  are  at  perfect  rest,  the  eye  is  accommo- 
dated to  see  clearly  at  all  distances  over  twenty  feet.  So 
distant  vision  requires  no  effort.  When  one  wishes  to  see 
an  object  less  than  twenty  feet  away  from  the  eye,  the 
muscles  must  cause  the  lens  to  become  more  curved. 
Thus  the  eye  can  see  clearly  up  to  about  five  inches  from 
the  eye.  Vision  is  best  when  the  object  is  about  ten 
inches  from  the  eye. 


/)t-=.-rirjr "^^^^^^-^V 


Diagram  of  the  eye  in  far  sight. 

The  lens  b  does  not  bring  the  rays  from  a  point  of  light  a  together  soon  enough. 
So  the  rays  fall  over  the  whole  surface  of  the  retina  from  d  to  e,  making  a  confused 
image  instead  of  a  clear  point.  When  the  rays  spread  less  apart,  as  when  the  light 
is  moved  farther  away,  to/;  the  lens  brings  them  together  sooner.  Then  the  rays 
fall  upon  a  single  point  of  the  retina  at^,  and  thus  form  a  clear  image. 

616.  Far  sight. — At  the  age  of  about  forty-five,  the  muscles  of 
the  lens  lose  some  of  their  power  of  contraction  and  are  unable  to 
make  the  lens  so  curved  as  in  youth.  Then  the  eye  cannot  be  adjusted 
for  near  vision,  while  for  far  vision  the  sight  is  as  good  as  ever.  So  an 
old  man  holds  his  newspaper  at  arms'  length.  He  also  aids  the  action 
of  his  lens  by  placing  before  his  eye  a  spectacle  lens  which  corrects 
the  deficiency  in  the  lens  of  his  eye. 

617.  Near  sight.  —  In  young  people  the  lens  often  brings  the 
rays  together  too  soon.     The  rays  must  be  made  more  diverging  by 


340 


APPLIED   PHYSIOLOGY 


bringing  *^he  object  very  near  the  eye.  Such  persons  cannot  see  dis- 
tinctly at  a  distance  greater  than  a  few  inches,  but  walk  about  as  in 
a  perpetual  tog. 


Diagram  of  the  eye  in  near  sight. 

The  lens  b  brings  the  rays  from  a  point  of  light  a  together  at  c  too  soon.  Sc 
the  rays  cross  and  fall  over  the  whole  surface  of  the  retina  from  d  to  e,  making  a 
confused  image  instead  of  a  clear  point.  When  the  rays  are  spread  apart  by 
bringing  the  light  near  the  eye,  as  at  f,  they  come  together  farther  away  upon  the 
other  side  of  the  lens,  as  at  g.  Thus  they  fall  upon  a  single  point  of  the  retina 
and  produce  a  clear  image. 

Near  sight  can  be  remedied  by  placing  in  front  of  the  eye  a  lens 
which  will  make  the  rays  more  diverging.  So  the  spectacles  have  the 
glasses  hollowed  out  instead  of  bulging. 

618.  Astigmatism  and  headaches.  —  Sometimes  the  lens  or 
cornea  is  more  curved  in  one  direction  than  in  another.  Then  a  part 
of  the  object  will  seem  distinct,  and  another  part  blurred,  and  the  eye 
muscles  will  constantly  change  the  focus  in  the  attempt  to  obtain  a  full 
and  clear  image.  This  is  very  tiresome  to  the  eyes,  and  often  causes 
severe  headaches.  The  remedy  is  to  use  a  glass  which  is  curved  in  one 
direction  only,  so  as  to  correct  only  the  defective  part  of  the  lens. 

619.  Cataract.  —  Sometimes  the  lens  becomes  hard  and  white. 
Then  no  light  can  pass  through,  and  there  is  total  blindness.  This  is 
called  a  cataract.  By  a  simple  and  safe  operation  the  lens  can  be 
removed,  when  the  light  will  fall  upon  the  retina  as  before.  Spectacles 
to  take  the  place  of  the  lens  enable  the  person  to  see. 

620.  Judgment  of  position.  —  In  perfect  vision  each  eye 
is  turned  toward  the  same  point,  so  that  the  images  fall 
upon  corresponding  points  of  the  retina.  But  the  two  eyes 
view  an  object  from  different  positions,  and  so  the  images 


THE   EYE  341 

are  not  exactly  alike.  The  blending  of  the  images  will 
give  the  idea  of  solidity  or  of  position  in  distinction  from 
the  impression  that  everything  is  a  flat  surface.  This  per- 
ception is  not  natural,  but  must  be  learned.  Distant  objects 
always  seem  flat. 

621.  Movements  of  the  eyes.  —  if  the  images  of  an  object  do 
not  fall  upon  corresponding  parts  of  the  retinas  of  the  two  eyes,  two 
images  will  be  seen.  Sometimes  a  muscle  will  draw  one  eye  aside  so 
that  it  does  not  look  in  the  same  direction  as  the  other  eye.  A  person 
with  this  defect  is  said  to  be  cross-eyed. 

Young  babies  have  no  control  of  their  eye  muscles,  and  so  have  no 
distinct  vision,  except  as  they  catch  accidental  glimpses.  A  bright 
cloth  gives  them  a  sensation  of  color  at  whatever  distance  it  is  held, 
and  so  amuses  them.  At  about  the  age  of  three  months  they  begin  to 
gain  control  of  their  muscles,  so  that  they  can  focus  the  eyes  and  turn 
them  to  any  object  at  will.  It  takes  them  several  months  more  to 
acquire  a  knowledge  of  solidity  and  position. 

Anything  touching  the  eye  causes  the  lids  to  close  in  a  reflex  man- 
ner for  protection.  Tears  flowing  over  the  eye  cause  the  lids  to  wink 
and  distribute  the  moisture  over  the  whole  surface. 

In  reading  in  the  cars,  the  constant  jarring  of  the  paper  compels  the 
muscles  of  the  eyes  to  be  in  constant  action  to  adjust  the  eye  to  the 
ever-varying  positions  and  distances.  So  they  soon  become  tired  and 
ache.  In  reading  while  lying  down,  the  eyes  must  look  toward  the 
feet.  The  constant  strain  of  turning  the  eyes  down  tires  the  muscles, 
so  that  the  vision  becomes  blurred. 

622.  Diseases  of  the  eye.  —  An  ulcer  or  scar  upon  the  cornea. 
closure  of  the  pupil,  cataract,  and  wasting  of  the  optic  nerve  are  com- 
mon causes  of  blindness.  The  conjunctiva  of  the  lids  may  become 
inflamed  and  run  matter,  or  may  become  raw  as  in  granulated  lids. 
All  matter  should  be  kept  from  the  eye  by  washing  it  off  with  borax 
water. 

A  particle  of  sand  or  other  substance  between  the  eyeball  and  the 
lids  causes  great  pain.  Rubbing  the  eyelid  forces  the  particle  into  the 
delicate  flesh  and  increases  the  pain.  If  the  lid  is  gently  held  away 
from  the  eyeball  for  a  moment,  the  tears  may  wash  out  the  particle. 

Blows  upon  the  eye  are  seldom  dangerous,  for  the  sclerotic  coat  is 
the  strongest  tissue  in  the  body. 


342  APPLIED   PHYSIOLOGY 

623.  Illusions  of  sight.  —  Irritating  the  optic  nerve 
excites  the  sensation  of  light.  A  blow  upon  the  head 
causes  a  sensation  of  seeing  bright  stars.  Pressure  upon 
the  eyeball  causes  a  sensation  of  a  ring  of  light. 

In  dreams,  sight  memories  return  to  consciousness  with 
all  the  vividness  with  which  they  were  first  made.  A 
crazy  man  may  imagine  the  face  of  the  clock  to  be  a 
man's  face  mocking  him,  and  so  he  may  attack  and 
destroy  it  To  insane  persons  of  a  religious  turn  of 
mind,  a  cloud  may  seem  to  be  an  angel  urging  them  on 
to  some  inspired  mission. 

624.  Effects  of  alcohol  and  tobacco. — Alcohol  weakens 
the  optic  nerves,  and  tends  to  cause  dimness  of  vision 
while  the  eyes  may  appear  healthy.  Tobacco  has  a  still 
greater  effect  upon  the  optic  nerve. 

625.  X  rays.  —  In  December,  1895,  a  kind  of  light  pro- 
duced by  electricity  was  discovered  which  can  penetrate 
wood,  flesh,  and  other  substances.  By  means  of  it  photo- 
graphs can  be  taken.  Although  it  makes  no  impression 
upon  the  retina,  yet  by  passing  it  through  certain  sub- 
stances the  rays  become  visible  to  the  eye.  Bone  is  pene- 
trated by  the  rays  with  greater  difficulty  than  flesh,  and 
so  they  can  be  photographed  and  seen  within  the  body. 
These  rays  cannot  be  bent  from  their  course,  and  so  can- 
not be  brought  to  a  focus  to  produce  a  real  image ;  but 
images  of  objects  are  formed  in  shadows,  due  to  the  vary- 
ing degrees  of  light  which  passes  through  different  objects. 
The  rays  are  sometimes  called  Rontgen  rays  from  their 
discoverer,  and  sometimes  simply  X  rays  because  of  their 
unknown  nature.  Practical  use  of  the  rays  is  made  in 
looking  within  the  body  so  as  to  determine  by  sight  the 
condition  of  the  bones  and  the  location  of  substances 
imbedded  in  the  flesh. 


A  foot  in  a  shoe. 
(From  an  X  ray  photograph.) 


344  APPLIED   PHYSIOLOGY 

626.    The  eye  in  lower  animals.  —  In  all  fourfooted  animals, 

and  in  birds,  reptiles,  and  fishes,  the  eyes  are  essentially  the  same  as  in 
man. 

Most  insects  possess  large  immovable  eyes  shaped  like  a  dome.  Each 
eye  is  made  up  of  many  smaller  eyes  like  a  honeycomb.     Each  little 

eye  contains  a  lens  which  forms  an  image 
upon  the  nerve  at  the  bottom  of  the  cavity. 
In  some  lower  forms  of  animals,  like  the 
leech,  there  is  a  spot  of  dark  coloring  matter 
under  the  skin  in  which  the  nerves  of  sight 
end.     Such  eyes  cannot  form  an  image,  on 
account  of  the  absence  of  the  lens,  but  a 
bright  light  or  a  shadow  of  a  large  object 
can   affect   the   nerve   and   give   the   leech 
The  eye  of  a  house  fly.         some  idea  of  its  surroundings.     Some  still 
a  eye,  made  of  many  small      lower  forms  of  animals  seem  to  be  able  to 
^^^^'  "    ■  recognize  light,  for  they  fold  themselves  up 

when  darkness  comes,  and  yet  they  have  nothing  which   at   all   re- 
sembles an  eye. 

Some  plants,  like  the  morning  glory,  are  affected  by  light,  for  their 
flowers  fold  themselves  at  night  and  open  again  when  the  sun 
rises. 

SUMMARY 

1.  Light  is  the  name  given  to  the  vibrations  of   a  very 

rare  gas  which  fills  all  space. 

2.  The  eye  is  like  a  photographer's  camera. 

3.  The  eye  is  set  deep  in  a  bony  socket,  called  the  orbit, 

and  is  protected  in  front  by  the  lids,  and  moistened 
by  tears. 

4.  .The  eye  can  see  distinctly  only  a  small  space  directly 

in  front,  but  can  distinguish  the  presence  of  objects 
in  a  full  half  circle. 

5.  A  sensation  of  sight  is  produced  instantly,  but  persists 

for  one  tenth  of  a  second  after  the  light  disappears. 

6.  Some  eyes  cannot  see  some  colors,  especially  red. 


THE  EYE  345 

7.  If  the  lens  cannot  bring  the  rays  of  light  together,  a 

person  is  far-sighted,  but  if  it  brings  the  rays  to- 
gether too  soon,  he  is  nem'-sigJited.  If  it  brings 
some  of  the  rays  together  sooner  than  others,  the 
condition  is  called  astigmatism. 

8.  If  the  lens  does  not  permit  light  to  pass  through,  the 

condition  is  called  a  cataract. 

"9.  By  means  of  the  two  eyes  viewing  an  object  from 
slightly  different  positions,  we  form  an  idea  of 
position  and  solidity. 

10.  If  one  of  the  muscles  of  the  eye  pulls  the  eyeball 
to  one  side,  the  person  is  cross-eyed  and  sees  two 
objects  instead  of  one. 

12.  Irritation  of  the  optic  nerve  causes  a  sensation  of  sight 
as  though  light  had  caused  the  impression.  Mem- 
ories of  sight  may  be  recalled  so  vividly  as  to  seem 
real,  as  in  a  dream. 

DEMONSTRATIONS 

135.  Examine  the  eyeball  of  a  calf  in  its  socket.  Carefully  sepa- 
rate the  eyeball  and  its  muscles  and  nerves  from  the  fat.  Notice  the 
cushion  of  fat  surrounding  the  whole  eyeball.  Notice  the  slender  mus- 
cles which  arise  from  the  back  part  of  the  orbit  and  are  attached  to  the 
outer  edge  of  the  eyeball.  Notice  the  optic  nerve  entering  the  middle  of 
the  back  side  of  the  eye.  Notice  other  nerves  and  the  numerous  blood 
tubes  which  cross  the  space.     Preserve  the  specimen  in  Muller's  fluid. 

136.  Procure  several  eyes  removed  from  their  sockets,  and  place 
some  in  MUllers  fluid  for  a  week  or  two,  and  examine  others  fresh. 

Notice  the  bulging  and  clear  cornea,  and  the  tough  white  sclerotic 
coat.  Holding  the  eye  with  its  cornea  tow^ard  you,  cut  it  completely 
into  halves.  Notice  the  aqueous  and  the  jellylike  vitreous  humors. 
Notice  the  curtain  of  the  iris  and  its  pupil.  Behind  the  iris  notice  the 
lens.  Remove  the  lens  and  note  its  shape  and  its  firm  consistency 
Notice  the  black  choroid  coat  lining  the  eyeball  next  to  the  sclerotic. 
Notice  the  thin  retina,  which  readily  separates  from  the  choroid. 


346  APPLIED    PHYSIOLOGY 

137.  With  a  common  magnifying  glass  show  how  a  convex  lens 
brings  rays  of  sunlight  to  a  focus.  Show  also  a  photographer's  camera. 
Show  the  image  which  appears  upon  the  ground  glass.  Then  compare 
the  camera  with  the  eye  specimen,  pointing  out  the  resemblances. 

138.  Have  the  students  look  steadily  at  a  line  of  print  and  tell  how 
much  they  can  read  without  moving  their  eyes.  An  inch  and  a  half 
will  be  all  they  can  see  at  once. 

Next  have  them  look  steadily  at  an  object,  and  notice  how  they  can 
see  dimly  all  objects  in  a  semicircle  about  them. 

139.  Illustrate  the  duration  of  impressions  by  spinning  a  square  top. 
It  will  appear  circular. 

140.  Illustrate  the  exhaustion  of  the  retina  by  having  the  students 
gaze  at  a  square  of  black  cloth  upon  a  white  paper.  After  a  moment 
let  the  students  look  steadily  at  the  wall,  when  a  square  spot  of  light 
will  appear,  for  the  part  of  the  retina  upon  which  the  image  of  the 
cloth  fell  is  less  exhausted  than  the  rest,  and  so  it  sees  the  light  from 
the  wall  more  clearly. 

141.  Illustrate  color  blindness  by  taking  a  sheet  of  light  pink  paper. 
Have  the  students  first  look  steadily  at  a  bright  red  object  in  a  strong 
light.  Then  gaze  at  the  pink  paper;  a  green  image  of  the  first  object 
will  appear,  showing  that  a  part  of  the  retina  has  become  exhausted  for 
the  red  rays,  but  can  still  see  other  colors. 

142.  Notice  the  pupil  of  the  eye  and  its  varying  size  in  diiferent 
lights.  Shade  another  person's  eyes  with  the  hands,  and,  quickly 
removing  them,  notice  that  the  pupils  grow  smaller.  Have  a  person 
look  steadily  at  your  finger  held  a  fev/  feet  in  front  of  the  eyes,  and 
then  quickly  bring  the  finger  near  the  eye  and  notice  that  the  pupil 
contracts  while  looking  at  it  near  by. 

143.  Illustrate  a  near-sighted  eye  by  holding  a  magnifying  glass  in 
front  of  the  eye,  which  is  the  same  as  increasing  the  power  of  the  lens. 
Notice  that  the  object  must  be  brought  nearer  the  eye. 

Show  a  double  concave  lens  and  explain  that  it  scatters  rays  and  so 
is  used  in  glasses  for  near  sight. 

144.  Illustrate  far  vision  by  looking  through  two  magnifying  glasses 
of  different  strengths.  Notice  that  the  weaker  glass  must  be  held 
farther  away  from  the  object. 

145.  Place  a  book  edgewise  before  the  eyes  and  notice  that  one  eye 
sees  one  side  and  the  other  eye  the  other  side. 

Now  examine  a  stereopticon  photograph  of  a  statue,  and  notice  that 


THE  EYE  347 

the  two  pictures  are  not  exactly  alike.  When  the  views  are  blended 
into  one  by  the  stereopticon,  the  image  seems  to  stand  out  like  a  real 
statue.  Explain  that  in  this  way  the  two  eyes  gain  a  knowledge  of 
position  and  solidity. 

146.  Illustrate  double  vision  by  pressing  one  eyeball  aside  while 
looking  at  an  object. 

147.  Have  a  person  gaze  at  your  finger  held  at  a  distance  from  his 
eye.  Now  bring  the  finger  near  the  eye,  and  notice  that  the  eyes  each 
turn  towards  the  nose  so  as  to  keep  directed  toward  the  object.  This  is 
the  only  manner  in  which  we  can  move  the  eyes  in  opposite  directions. 

148.  Press  hard  upon  the  closed  eyelids.  Notice  the  ring  of  fight 
which  appears.  Explain  that  this  is  due  to  the  irritation  of  the  optic 
nerve. 

149.  Test  the  individual  members  of  the  class  for  color  blindness 
by  showing  them  shades  of  red,  green,  and  yellow,  telling  them  to 
match  the  shades  and  arrange  them  in  order.  Also  test  the  power  of 
vision  ot  the  individual  members  of  the  class  by  placing  before  them 
printing  with  letters  of  various  sizes.  Have  each  pupil  read  as  far  as 
he  can,  all  standing  at  the  same  distance. 


REVIEW  TOPICS 

1.  Describe  light;  color;  focus;  and  the  effects  of  light 

in  a  photographer's  camera. 

2.  Show  that  the  eyeball  is  like  a  photographer's  camera, 

describing   its   outer    coverings ;    its   retina ;    nerve ; 
cornea ;  iris,  pupil,  and  lens. 

3.  Describe    the    orbit  ;    eyelids  ;   the    lachrymal    gland  ; 

tears,  and  the  tear  ducts. 

4.  Show  that  a  person  can  see  more  clearly  directly  in 

front  of  his  eyes  than  upon  either  side. 

5.  Show  that  the  duration  of  a  sight  sensation  changes 

the  appearance  of  moving  objects. 

6.  Describe  color  blijidiiess. 

7.  Show  that  the  retina  may  become  unable  to  act  from 

overwork,  as  by  gazing  at  bright  objects;  at  colored 


348  APPLIED   PHYSIOLOGY 

objects;  and  by  a  light  in  front  of  the  unshaded 
eyes. 

8.  Show  that  the   iris    protects  the  retina   against   too 

strong  Hght. 

9.  Show  that  the  lens  must  change  its  shape  to  accom- 

modate itself  to  near  vision  and  to  far  vision. 

10.  Tell  the  condition  of  the  lens  and  the  remedy  mfar 

sight ;  in  near  sight ;  and  in  astigmatism. 

11.  Describe  a  cataract  and  its  remedy. 

12.  Show  how  two  eyes  aid  in  the  judgment  of  form  and 

position. 

13.  Describe  the  condition  of  the  eye  muscles  in  a  cross- 

eyed person,  and  tell  how  vision  is  affected. 

14.  Show  how  reading  upon  a  moving  railway  train  and 

reading  while  lying  down  overwork  the  eye  mus- 
cles. 

15.  Tell  how  to  care  for  an  eye  which  runs  matter,  and 

how  to  remove  a  speck  of  dirt  from  under  the  lid. 

16.  Show  that  rubbing  a  sore  eye  is  always  liable  to  do 

harm. 

17.  Show  that   irritation  of   the    eye    may  produce  false 

sensations  of  sight ;  and  that  sight  memories  may 
seem  to  be  real  again. 

18.  Describe  the  X  rays. 

19.  Describe  the  effects  of  alcohol  and  tobacco  on  the 

eye. 

20.  Describe  the  eye  in  lower  animals;  in  insects;  and  in 

a  leech. 


CHAPTER   XXXVI 


THE  VOICE 


627.  The  larynx.  —  The  basis  of  the  voice  is  a  sound 
made  in  the  larynx  during  expiration.  The  larynx  is  a 
triangular  box  about  three  quarters 
of  an  inch  across,  made  of  cartilages. 
It  connects  the  trachea  and  pharynx. 
Its  two  sides  are  formed  of  a  flat 
cartilage,  bent  sharply  backward, 
and  called  the  thyroid  cartilage. 
The  upper  end  of  the  fold  projects 
slightly  from  under  the  chin  and  is 
called  the  Adams  apple.  Under- 
neath the  thyroid  cartilage  is  a  cir- 
cular cartilage  whose  back  part  pro- 


—  a 


Back  view  of  the  larynx. 


c  movable  cartilage  for  the 
attachment  of  the  vocal 
cords. 


a   thyroid  cartilage, 

jects  upward  so  as  partly  to  nil  m   b  vocal  cords. 

space  between   the   back  edges   of 

the  thyroid  cartilage.     In  form  and 

size  it  resembles  a  lars^e  finsrer  rins:,   ^  cricoid  cartilage. 

f  ^  ^^    e    epiglottis. 

and  is  called  the  cricoid  cartilage. 

On  top  of  the  back  part  of  the  cricoid  cartilage  are  two 
small  cartilages,  shaped  like  triangular  pyramids,  and  so 
arranged  that  they  can  turn  sidewise.  One  lower  corner 
of  each  projects  forward.  From  it  a  flat  band  extends 
across  the  larynx,  and,  with  its  fellow  from  the  opposite 
side,  attaches  itself  to  the  lower  part  of  the  thyroid  carti- 
lage.    Muscles   can  tighten   them  and  bring  them  close 

349 


350 


APPLIED   PHYSIOLOGY 


together.  Expiring  air  between  these  bands,  while  they 
are  tight  and  close  together,  causes  them  to  vibrate  and 
produce  a  sound  which  is  called  the  voice.     Hence  the 


Top  view  of  the  larynx,  with  the 
vocal  cords  closed,  as  in  speaking. 

a   epiglottis.        b   vocal  cords. 


Top  view  of  the  larynx,  with  the 
vocal  cords  open,  as  in  breathing. 

a  epiglottis.        b  vocal  cords. 


bands  are  called  the  vocal  cords.  The  whole  larynx,  ex- 
cept the  edges  of  the  vocal  cords,  is  covered  with  loose 
mucous  membrane. 

628.  Pitch  of  the  voice.  —  All  sound  has  the  four  char- 
acteristics of  pitch,  intensity^  quality,  and  duration.  The 
same  characteristics  apply  to  the  voice. 

Pitch  depends  upon  the  number  of  vibrations  which 
occur  each  second.  In  order  that  the  vibrations  of  the 
air  shall  blend  into  a  musical  note  they  must  occur  at  the 
rate  of  sixteen  times  a  second,  but  until  they  reach  a  rate 
of  fifty  the  sound  is  more  like  a  buzz  than  music.  Upper 
C  of  the  bass  voice  which  corresponds  to  lower  C  of  a 
soprano,  is  produced  by  256  vibrations  per  second.  The 
shorter  or  tighter  the  vocal  cords  are,  the  higher  will  be 
the  pitch.  In  men  the  cords  are  longer  than  in  women, 
making  a  man's  voice  an  octave  lower  in  pitch.  The 
larynx  and  voice  of  a  boy  resemble  those  of  a  girl.  At 
about  the  age  of  fifteen  the  voice  of  a  boy  becomes  like 
a  man's,  while  in  a  girl  it  remains  unchanged. 

629.  The  intensity  of  the  voice  depends  upon  the  force 
with  which  air  is  expelled  through  the  larynx.     In  making 


THE  VOICE  351 

a  very  loud  sound,  the  great  force  of  the  air  current  causes 
the  vibrations  of  the  vocal  cords  to  be  painful. 

630.  The  muscles  of  the  larynx  will  grow  strong  by  judicious  .prac- 
tice, so  that  a  person  can  be  heard  across  a  hall  in  which  he  formeily 
could  not  be  heard  a  few  feet  away.  If  the  voice  becomes  huskv,  or 
causes  a  cough,  or  if  the  throat  begins  to  feel  painful,  the  vocal  coids 
are  being  overworked  and  should  be  rested. 

631.  Quality  of  the  voice.  — A  string  stretched  between 
the  hands  produces  a  faint  unpleasant  sound ;  but  if  it  is 
stretched  over  a  hollow  box,  like  the  body  of  a  violin,  the 
whole  box  will  vibrate  and  greatly  magnify  the  sound  and 
also  will  make  it  full  and  pleasant. 

The  vibrations  of  the  vocal  cords  alone  produce  a  faint 
and  almost  squeaking  sound  very  unlike  that  of  the  voice ; 
but  belov/  the  larynx  are  the  hollow  trachea  and  lungs. 
Above  it  are  the  hollow  mouth,  nose,  and  frontal  sinuses. 
All  these  vibrate  with  the  vocal  cords,  and  so  the  quality 
of  the  voice  is  modified.  Each  person's  voice  has  a  peculiar 
quality  of  its  own  which  is  at  once  recognized. 

When  a  person  sings  with  the  nose  stopped,  we  say 
that  he  sings  through  the  nose.  In  reality,  a  nasal  voice 
is  due  to  the  absence  of  vibrations  in  the  nose. 

632.  Ventriloquism.  —  The  quality  of  sound  is  modified  by 
distance,  so  that  one  can  judge  accurately  whence  it  comes.  It  is 
possible  to  imitate  the  quality  of  distant  sounds,  so  that  there  seems  to 
be  another  person  talking  in  a  remote  part  of  the  room  or  inside  of  the 
real  talker.     This  is  called  veiitriloqiiisjn. 

633.  Speech.  —  Speaking  consists  mainly  in  rapid  changes 
in  the  quality  and  duration  of  vocal  sounds.  In  singing  or 
crying  out,  single  sounds  are  more  or  less  prolonged,  but 
in  forming  spoken  words,  the  sounds  are  cut  off  by  the 
tongue  and  lips  several  times  a  second.  It  is  not  even 
necessary  to  form  a  sound  with  the  larynx.     In  whispering, 


352  APPLIED   PHYSIOLOGY 

air  is  simply  breathed  through  the  mouth,  while  the  tongue 
and  lips  cut  it  off  at  intervals  as  though  a  sound  were 
being  made. 

634.  A  simple  sound  continuously  uttered  is  a  vowel 
sound.  If  the  mouth  is  simply  opened  without  effort,  the 
sound  formed  will  be  that  of  a  as  in  father.  When  the 
mouth  is  closed  the  most,  it  forms  the  sound  oo  as  in  room. 
A  consonant  sound  is  a  vowel  sound  suddenly  modified  in 
either  its  beginning  or  ending.  For  instance,  when  the 
tip  of  the  tongue  is  held  against  the  palate  just  back  of  the 
teeth,  and  a  vowel  sound  is  begun  by  forcibly  blowing  it 
away,  the  sound  will  be  either  /,  d^  or  th. 

635.  Rate  of  talking.  —  A  public  speaker  will  ordinarily  utter 
125  words  a  minute.  On  an  average  each  word  will  be  composed  of, 
at  least,  four  different  sounds.  Thus  the  vocal  organs  must  make  600 
separate  adjustments  each  minute,  or  10  each  second. 

636.  Relation  of  sound  and  speech.  —  Words  spoken  must 

first  be  heard.  So  no  matter  what  the  race  of  a  child,  it  will  speak 
exactly  the  speech  which  it  hears.  If  a  child  is  brought  up  in  com- 
pany with  an  ignorant  nurse  girl,  its  speech  will  be  her  brogue.  On 
the  other  hand,  if  the  child  is  brought  up  among  educated  and  refined 
persons,  it  will  speak  an  elegant  tongue. 

A  deaf  person  has  great  difficulty  in  learning  to  speak  at  all,  for  he 
can  have  no  idea  of  the  sound  which  he  should  make.  Without  special 
instruction  deaf  persons  would  never  learn  to  speak  at  all,  but  by  letting 
them  see  or  feel  the  position  of  the  lips  and  tongue  in  forming  words, 
they  learn  to  place  their  own  parts  in  the  same  position  and  so  finally 
learn  to  talk. 

637.  Necessity  of  the  tongue  in  speech.  —  The  tongue  is 

usually  considered  to  be  so  necessary  in  speech  that  the  language  itself 
is  called  a  tongue.  As  man's  mouth  is  constructed  the  tongue  does  do 
the  most  important  part  of  forming  words,  but  if  the  organ  is  removed 
as  far  back  as  possible,  the  stump  can  still  form  intelligible  words. 
Sometimes  the  front  part  of  the  tongue  is  bound  down  or  "  tied  "  so 
that  it  cannot  move  so  freely  as  it  should.  This  is  supposed  to  hinder 
a  child  in  talking,  but  in  reality  it  does  not. 


THE  VOICE  353 

638.  Benefits  of  vocal  exercise.  —  In  singing  and  lec- 
turing, the  breathing  must  be  regular  and  deep.  The 
abdominal  muscles  must  act,  and  often  a  sound  must  be 
prolonged  until  the  air  in  the  lungs  is  exhausted.  The 
respiratory  muscles  must  act  continuously  and  strongly 
and  for  long  periods  of  time.  Thus  an  increased  amount 
of  oxygen  will  be  taken  into  the  body.  Voice  training  is 
one  of  the  best  modes  of  exercise,  especially  for  a  weak 
person  who  cannot  endure  long  walks  or  gymnastic  exer- 
cises. It  is  all  the  more  valuable  because  a  person  does 
not  think  of  the  exercise,  but  directs  the  mind  to  an  inter- 
esting and  useful  occupation. 

639.  Diseases  of  the  larynx.  —  In  a  cold  in  the  throat 
the  mucous  membrane  becomes  tender  and  swollen.  Then 
the  movements  of  the  vocal  cords  are  impeded  and  painful, 
so  that  only  a  hoarse  sound,  or  no  sound  at  all,  can  be 
produced.  By  repeatedly  overworking  the  vocal  cords, 
they  and  the  muscles  of  the  larynx  become  flabby  and 
tender  so  that  their  vibrations  are  painful  or  impossible. 
Then  the  voice  is  reduced  to  a  whisper.  Sometimes  the 
nerves  of  the  larynx  are  paralyzed  so  that  no  motor  orders 
can  reach  the  muscles.     Then  no  sound  can  be  formed. 

• 

640.  In  mouth  breathing,  the  air  is  drawn  directly  into  the  larynx 
without  being  purified,  warmed,  and  moistened  in  the  nose.  This  irri- 
tates the  lar}'nx  and  vocal  cords  so  that  the  voice  is  made  weaker  and 
harsher.  A  mouth  breather  can  seldom  become  a  good  singer  or 
speaker. 

641.  Tobacco. — Tobacco  smoke  may  produce  such  an 
irritation  that  there  is  a  constant  hacking  cough.  Cigar- 
ettes are  especially  bad  for  the  voice,  for  the  smoke  is 
deeply  inhaled.  Alcohol  interferes  with  the  voice  by 
inducing  indigestion  and  weakness  of  the  muscles. 

ov.  PHYSIOL.  —  23 


354  APPLIED   PHYSIOLOGY 


SUMMARY 

1.  The   larynx   is   a   box  of  cartilage  across  which  two 

strong  bands  called  vocal  cords  are  stretched. 

2.  When  the  vocal  cords  are  tightened  and  air  is  expelled 

between  them,  a  sound  called  the  voice  is  made. 

3.  The  pitch  of  the  voice  will  depend  upon  the  tightness 

and  length  of  the  cords. 

4.  The  intensity   of   the   voice   depends  upon  the  force 

with  which  the  air  is  expired. 

5.  The  quality  of  the  voice  is  imparted  to  it  by  vibrations 

of  the  air  in  the  lungs,  mouth,  and  nose. 

6.  In  speech  sounds  are  modified  mainly  by  the  lips  and 

tongue. 

7.  A  man  must  first  hear  the  sound  of  speech,  and  then 

learn  to  imitate  it.     Special  means  must  be  employed 
to  teach  a  deaf  person  to  talk. 

8.  If   the   vocal    apparatus   is   overworked    or    becomes 

inflamed,  the  voice  is  injured. 

DEMONSTRATIONS 

150.  Procure  a  larynx  from  a  butcher^s  shop.  Notice  the  large  flat 
thyroid  cartilage,  and  under  it  the  ring-shaped  cricoid  cartilage.  Notice 
the  white  vocal  cords  passing  forward  to  the  lower  part  of  the  thyroid. 
Notice  the  loose  mucous  membrane  above  the  vocal  cords.  Grasp  the 
thyroid  cartilage  so  as  to  move  the  cricoid  forward  and  backward,  and 
note  how  the  movements  tighten  and  relax  the  vocal  cords.  Notice 
the  muscles  which  move  the  larynx.  Test  the  pyramidal  cartilages  to 
which  the  vocal  cords  are  attached. 

151.  If  po.ssible,  get  a  physician  to  show  the  vocal  cords  in  action 
upon  a  living  person.  He  will  do  it  by  means  of  a  small  mirror  held 
in  the  back  part  of  the  mouth. 

152.  Have  the  pupils  feel  each  other's  chests  while  counting  one, 
two,  three,  and  note  the  marked  vibrations.     In  the  same  way  feel  of 


THE   VOICE 


355 


the  larynx  and  of  the  nose  and  teeth.  Explain  that  these  vibrations 
also  produce  sound  and  give  quality  to  the  sound  in  the  larynx.  Then 
compress  the  nose  and  note  the  nasal  quality  of  the  voice. 

153.  Show  how  the  different  vowel  sounds  are  formed.  Make  a  con- 
tinuous sound  as  of  e  in  7ieed.  Without  changing  the  pitch  or  intensity 
change  the  mouth  to  a  position  to  utter  in  succession  the  sounds  a  as 
in  jnade,  a  as  in  7nal,  ch  as  in  father,  0  as  in  note,  and  00  as  in  r 00771. 
Note  how  the  sounds  glide  into  each  other. 

154.  Note  the  positions  of  the  tongue  and  lips  in  uttenng  the 
different  consonant  sounds.  Note  that  p,  b,  and  f  are  formed  much 
alike  ;  and  also  k,  ch,  and_^;  and  t,  d,  and  th. 

155.  Show  how  some  lower  animals  and  insects  produce  sounds. 
Have  the  pupils  notice  how  a  canary  bird  swells  his  throat  in  singing, 
and  explain  that  this  is  because  it  has  two  or  three  pairs  of  vocal  cords. 

Upon  the  backs  of  a  katydid's  wings  show  the  drumheads,  which, 
when  rubbed  together,  produce  its  sound.  Show  that  a  fly's  buzz  is 
due  to  the  exceedingly  rapid  motion  of  its  wings. 

REVIEW  TOPICS 

1.  Describe  the  larynx. 

2.  Show  how  the  vocal  cords  produce  sound. 

3.  Show  how  tYiQ pitch  of  the  voice  can  be  changed. 

4.  Show  how  the  intensity  of  the  vocal  sounds  can  be 

changed. 

5.  Show  how  the  quality  of  the  voice  is  modified. 

6.  Describe  ve^itriloqnism. 

7.  Show  that  speech  depends  upon  modifications  in  the 

duration  and  mode  of  production  of  vocal  sounds. 

8.  Show  the  relation  between  speech  and  hearing. 

9.  Show  that  the  tongue  is  not  absolutely  necessary  in 

speech. 

10.  Show  how  vocal  exercise  benefits  the  whole  body. 

11.  Show  how  inflammation    of   the    larynx   and   taking 

certain  things  into  the  mouth  injure  the  voice. 


Bones  of  the 


Clavicle,  or  Collar  Bone 


Sternum,  or  Breastbone.  -, 


Ribs. 


Pelvis,  including  (5.)  Sacrum  and 
(Cx.)  Coccyx. 


Patella 


Tibia,  or  Large  Bone  of  Fore  Leg, 


Head  and  Face. 


Bones  of  Vertebral  Column. 


Scapula,  or  Shoulder  Bone. 


Humerus. 


■Ulna. 


Radius. 

-Carpus,  or  Wrist.  —  Eight 

small  bones. 
Hand.  —  Nineteen  bones. 


Femur. 


Tarsus,  or  Ankle  and  Heel  Bones  (7). 
Bones  of  foot.  —  Nineteen  bones. 


Fibula,  or  small  Splint  Bone  of  Leg. 


The  human  skeleton,  showing  position  of  bones. 

356 


CHAPTER   XXXVII 
BONES. 

642.  Use  of  bone.  —  Bones  give  shape  and  support  to 
the  body  and  impart  to  it  strength  and  stiffness.  Like 
beams  of  the  strongest  oak,  they  extend  the  length  of 
every  limb,  and  form  arches  for  the  protection  of  the 
organs  in  the  head,  chest,  and  abdomen.  They  are  of  va- 
rious sizes  and  shapes,  as  are  suited  to  the  different  parts. 
In  the  whole  body,  about  tw6  hundred  are  jointed  together 
to  form  its  framework,  called  the  skeleton. 

643.  The  skeleton.  —  Eight  rounded  plates  of  bone  form 
the  top  of  the  head,  and  fourteen  of  irregular  shape  form 
the  face.     Together,  they  form,  the  skull. 

Twenty-six  irregular  rings  of  bone  piled  one  upon  the 
other  form  a  support  for  the  trunk  of  the  body.  It  is 
called  the  backbone  or  spinal  column,  or  simply  the  spine. 
The  lowest  bone  is  called  the  coccyx,  and  the  one  next 
above  it,  the  sacrtim.  Each  ring  of  bone  is  called  a  verte- 
bra. The  spine  is  made  of  a  series  of  small  bones  so  that 
it  can  bend  without  breaking.  It  is  gently  curved  so  as  to 
lessen  the  jarring  in  running  and  other  violent  movements 
of  the  body. 

From  the  vertebrae,  beginning  at  the  eighth,  twelve  pairs 
of  bones  called  ribs  curve  around  the  body.  In  front  they 
join  a  flat  bone  called  the  sterjiuni  or  breastbone.  They 
inclose  and  protect  the  heart  and  lungs. 

Each  shoulder  is  formed  in   front  by   a    slender   bone 

357 


358 


APPLIED   PHYSIOLOGY 


called  the  collar  bone  or  clavicle^  and  behind  by  a  flat  bone 
called  the  shoulder  blade  or  scapula.  Their  outer  ends 
meet  and  form  a  support  for  the  arm. 

The  upper  arm  has  one  long  bone 
called  the  hiimenis.  The  forearm  has  a 
long  bone  on  its  thumb  side  called  the 
radius,  and  another  on  its  little  finger  side 
called  the  tdna.  The  wrist  has  eight 
rounded  bones  called  carpal  bones.  The 
palm  of   the   hand   has  five  long  bones 


The  pelvis. 

called  metacaipal  bones.    The  fingers  have 
fourteen  slender  bones  called  phalanges. 

Two    irregular   and    massive    rings    of 
bone  form  the  hip  bones.     With  the  sa- 
crum they  form  a  ring  called  the  pelvis. 
The   body  sits  upon    the   lower   part  of 
each    hip   bone.     The    pelvis  forms    the 
bottom  of  the  abdomen. 
The  bones  of  the  leg  have  nearly  the   same   plan  and 
arrangement  as  those  of  the  arm.     The  thigh  has  one  long 
bone  called  the  femur.     In  front  of  the  knee  is  a  flat  bone 


The  spinal 
column. 


BONES  359 

called  the  patella.  The  shin  is  formed  by  one  long  bone 
called  the  tibia,  upon  the  outside  of  which  is  a  very  slender 
bone  called  the  fibula.  The  lower  end  of  the  fibula  forms 
the  outer  ankle  bone,  while  a  projection  from  the  tibia 
forms  the  inner  ankle  bone. 

Seven  rounded  bones,  called  tarsal  horiQS,  form  the  instep 
of  the  foot.  Five  slender  bones  beyond  them,  called  meta- 
tarsal bones,  form  the  ball  of  the  foot.  The  tarsal  and  meta- 
tarsal bones  are  bound  together  so  as  to  form  an  arch 
which  bears  upon  the  ground  only  at  the  heel  and  ball  of 
the  foot.  The  arch  is  somewhat  elastic  and  prevents  jar- 
ring of  the  body  in  walking.  It  sometimes  becomes  flat- 
tened, producing  the  painful  deformity  called  fiat  foot. 
Fourteen  slender  bones,  called  phalanges,  form  the 
toes. 

644.  Structure  of  bones.  —  Bones  are  dense  and  brittle 
upon  the  outside.  All  are  covered  with  a  very  tough  mem- 
brane, called  Xho,  periosteimt.  In  flat  or  rounded  bones  the 
hard  outside  surfaces  are  scarcely  thicker  than  paper,  and 
the  two  surfaces  are  connected  together  by  a  network  of 
bone  which  looks  like  a  honeycomb,  and  is  called  cancel- 
lous bone. 

In  long  bones,  the  central  shaft  is  composed  of  a  thick 
shell  of  hard  bone  surrounding  a  cavity  filled  with  fat; 
their  ends  consist  of  a  thick  shell  of  hard  bone  covering  a 
large  mass  of  cancellous  bone. 

A  bone  is  about  twice  as  strong  as  a  piece  of  oak  of  the  same  size. 
It  is  elastic  and  can  bend  considerably  without  breaking.  Any  given 
weight  of  a  substance  is  stronger  when  made  into  a  hollow  shaft,  like 
a  bicycle  frame,  than  when  formed  into  a  solid  rod  of  the  same  length. 
So  the  strength  of  a  bone  is  still  further  increased  by  its  being  either 
hollow,  as  in  the  shaft  of  a  long  bone,  or  else  braced  with  cancellous 
bone,  as  in  a  flat  bone  and  the  ends  of  a  long  bone. 


36o 


APPLIED  PHYSIOLOGY 


645.  Microscopic  appearance.  —  Bone  is  composed  of 
branching  connective  tissue  cells  and  fibers,  which  are 
arranged  in  circles  around  minute  tunnels  called  Haversimi 
canals.  Each  Haversian  canal  contains  arteries,  veins, 
and  nerves.  Lime  is  mixed  with  the  cells  and  canals  like 
starch  among  the  fibers  of  linen,  and  imparts  to  them  their 


a  bone  cells. 


Thin  slice  of  bone  (x  200). 
b   Haversian  canal,  containing  blood  tubes  and  nerves. 


hardness  and  rigidity.     Lime  forms  about  two   thirds  of 
the  bone  by  weight. 

646.  The  periosteum  carries  arteries  and  nerves  which 
enter  minute  openings  in  the  bone.  During  childhood,  or 
when  a  bone  is  diseased,  the  cells  of  its  inner  layer  are 
very  active  in  reproducing  themselves  and  in  forming  new 
bone.  Bone  stripped  of  its  periosteum  is  apt  to  die, 
but  when  the  bone  dies  the  periosteum  usually  remains 
alive  and  soon  reproduces  new  bone.  The  periosteum 
also  affords  an  attachment  for  muscles. 

647.  Cartilage.  —  The  bones  of  very  young  animals 
contain  little  or  no  lime,  but  are  soft  and  pliable.     In  this 


BONES  361 

condition  they  are  called  cartilage.  As  age  advances, 
lime  is  deposited  among  the  cells,  and  they  become  hard 
and  brittle,  forming  true  bone.  A  layer  of  cartilage  re- 
mains to  cover  the  ends  of  most  bones.  Late  in  life  it 
may  take  up  lime  aad  so  become  like  bone. 

648.  Rickets.  —  Sometimes  a  child's  bones  contain  too  little  lime  ; 
then  under  the  influence  of  continual  pressure  of  standing,  the  bones  of 
the  leg  may  gradually  grow  into  a  bowed  shape.  This  disease  is  called 
rickets,  and  is  due  to  too  little  nourishment.  When  fed  on  a  sufficient 
amount  of  proper  food,  the  bones  soon  grow  rigid  again,  and  as  the 
child's  legs  grow  longer,  their  curves  become  less  noticeable. 

649.  Broken  bones.  —  Bones  are  often  broken.  Then 
the  cells  are  injured,  and  blood  tubes  and  nerves  are  torn 
across.  So  there  will  be  great  pain  and  tenderness.  When 
a  bone  is  broken,  its  cells  reproduce  themselves  and  fill  in 
the  space  with  new  connective  tissue.  In  course  of  a 
few  weeks,  lime  is  deposited  in  the  new  tissue,  and  the 
union  is  complete.  When  a  bone  is  broken,  the  surgeon 
pulls  its  ends  in  place  and  binds  them  to  stiff  splints  until 
healing  is  complete. 

If  a  bone  is  broken,  the  Hmb  should  be  at  once  bound  to  a  board  or 
stick  with  handkerchiefs  or  strips  of  cloth.  Take  care  not  to  tie  the 
bands  tightly  enough  to  stop  the  flow  of  blood. 

As  a  person  grows  older,  more  lime  is  deposited  in  his  bones,  and 
they  become  harder  and  more  brittle.  Then  they  are  more  likely  to  be 
broken  and  are  less  able  to  grow  together  again.  Often  a  child's  bone 
will  bend  until  it  breaks,  but  its  ends  still  hold  together  like  a  broken 
green  stick.     In  older  people  it  snaps  like  a  dry  twig. 

650.  Diseases  of  bones.  —  Bruises  or  consumption  or  other 
causes  of  disease  may  produce  inflammation  and  abscesses  of  the  bone 
as  in  any  other  part  of  the  body.  Then  the  bone  is  very  painful  and 
tender  and  may  die.  Then  the  periosteum  will  form  a  new  bone.  If 
a  large  piece  of  bone  dies,  it  wastes  away  more  slowly  than  new  bone 
is  formed.     All  fourfooted  animals  have  nearly  the  same  bones  arranged 


362  APPLIED    PHYSIOLOGY 

in  the  same  way  as  man.  A  bird's  wing  is  bone  for  bone  almost  like  a 
man's  arm  and  hand.  A  turtle's  shell  is  its  ribs,  while  the  bones  of  its 
limbs  are  like  those  of  man. 

SUMMARY 

1.  About  200  bones  give  the  body  form  and  strength. 

2.  The  outside  of  all  bone  is  a  hard  plate,  while  the  inside 

is  either  a  fine  network  of  bone  or  else  is  hollow. 

3.  The  hollow  form  of  bone  combines  strength  with  light- 

ness. 

4.  Bone  is  composed  of  living  cells  and  fibers  nourished 

by  arteries  and  endowed  with  sensibility  by  nerves. 
Lime  is  mixed  with  the  cells  like  starch  with  linen. 

5.  Bone  is  covered  with  a  tough  membrane  called  thQ peri- 

osteum, which  carries  the  blood  tubes  and  nerves  to 
the  bone,  and  forms  new  bone  during  the  period  of 
growth  or  when  the  bone  is  diseased. 

6.  Cells  and  fibers  resembling  those  in  bone,  but  contain- 

ing no  lime,  form  cartilage. 

DEMONSTRATIONS 

156.  Show  a  complete  skeleton  of  at  least  a  small  animal.  Point 
out  the  different  shapes  of  the  bones  and  how  they  are  adapted  to  their 
positions  and  work.  Point  out  in  the  living  body  where  the  different 
bones  can  be  felt. 

157.  Procure  a  fresh  beef  bone,  and  another  similar  one  dried.  Note 
the  bright  pink  color  of  the  fresh  bone,  and  the  white  or  brown  color 
of  the  dried  specimen.  Notice  that  the  periosteum  can  be  stripped 
from  the  bone.  Notice  the  soft  cartilage  which  covers  the  ends  of  the 
bone. 

158.  Saw  a  long  bone  in  two  crosswise  and  then  saw  one  half  in  two 
lengthwise.  Notice  the  hollow  cavity  in  the  shaft  of  the  bone  and  the 
fat  or  marrow  which  fills  it.  Notice  the  honeycombed  appearance  of 
the  inside  of  the  ends  of  the  bone. 

159.  Procure  a  specimen  of  bone  mounted  for  the  microscope. 
Using  a  power  of  at  least  fifty  diameters,  notice  the  circles  of  bone  cells 


BONES  363 

and  the  numerous  fine  branches  of  the  cells.  Notice  the  Haversian 
canal  in  the  center  of  each  circle.  Examine  also  a  specimen  of 
cartilage. 

160.  Procure  two  slender  bones  which  are  exactly  alike.  Place  one 
in  a  hot  fire  for  a  few  hours.  This  will  burn  out  the  cells  and  fibers 
and  leave  only  the  lime.  The  bone  is  now  very  brittle  and  easily  crum- 
bles to  pieces.  Place  the  other  in  a  bottle  containing  one  part  of 
muriatic  acid  and  ten  of  water.  After  a  week  this  acid  will  have 
removed  the  lime,  leaving  only  the  cells  and  fibers.  The  bone  can  now 
be  twisted  and  bent  like  a  piece  of  flesh. 

161.  Boil  a  leg  bone  of  a  half-grown  animal  until  the  flesh  is  re- 
moved. Notice  that  a  disk  of  cartilage  extends  nearly  through  the 
shaft  very  near  the  ends.  Possibly  the  end  beyond  it  will  come  off. 
Explain  that  the  cartilage  forms  new  bone  which  increases  the  length 
of  the  shaft  as  long  as  the  bone  continues  to  grow. 

REVIEW  TOPICS 

1.  Show  why  bones  are  needed  in  the  body. 

2.  Describe  the  bones  of  the  skull;  of  the  spine;  of  the 

ribs;  of  the  arms;  of  the  pelvis;  and  of  the  legs. 

3.  Describe  the  appearance  of  a  bone  when  sawed  in  two 

both  lengthwise  and  crosswise. 

4.  Show  the   advantage  of  having  some  of  the  bones 

hollow. 

5.  Describe  the  microscopic  appearance  of  bone. 

6.  Give  the  uses  of  periosteum. 

7.  Describe  cartilage. 

8.  Describe  the  changes  which  occur  in  bones  with  ad- 

vancing age. 

9.  Describe  rickets. 

10.  Describe  the  condition  of  a  bone  when  broken,  and 

tell  how  it  is  repaired,  and  how  to  care  for  a  broken 
limb. 

11.  Show  how  a  bone  can  become  inflamed  ;  and  how  dead 

bone  is  replaced. 


CHAPTER   XXXVIII 


JOINTS 


651.  Kinds  of  joints.  — The*  union  of  two  bones  is  called 
a  joint.  Some  bones  grow  together  and  form  a  single 
rigid  bone,  while  others  are  joined  together  only  by  loose 
fibrous  tissue  which  permits  the  joints  to  bend  freely. 
Between  these  two  extremes,  joints  possess  all  gradations 
of  movement. 

652.  Inflexible  joints.  —  Some  bones  of  the  skull  are 
joined  together  by  cartilage  during  childhood.     Later  in 

life,  when  growth  ceases,  the  cartilage 
becomes  bone  and  unites  the  two  bones 
into  a  single  one. 

Other  bones  of  the  skull  are  dove- 
tailed with  each  other,  so  that  while 
they  can  move  slightly,  they  cannot  be 
separated.  The  thick  bones  of  the  top 
of  the  skull  are  united  in  this  way. 

Between  the  separate  bones  of  the 
pelvis  and  between  the  vertebrae  there 
are  large  pads  of  fibrous  tissue,  almost 
like  cartilage.  These  pads  permit  slight 
movements  between  the  bones  and  so 
prevent  jarring  during  violent  move- 
ments of  the  body.  They  are  usually  stronger  than  bone 
itself,  so  that,  by  pulling  or  bending,  the  bones  will  be 
torn  apart  rather  than  the  pads. 

364 


1-- 


Hinge  joint  of  the  elbow 
I   humerus.  2   ulna. 


JOINTS  365 

Between  the  ends  of  the  ribs  and  the  sternum  there  are 
cartilages  of  the  shape  of  the  ribs.  In  old  age  they  often 
take  up  lime  and  become  real  bone. 

653.  Flexible  joints.  — The  joints  of  the  head  and  trunk 
of  the  body  are  mostly  inflexible,  while  those  in  the  limbs 
permit  very  free  movements  of  the  bones.  In  flexible 
joints  the  bones  are  held  together  by  a  strong  fibrous 
membrane  called  a  ligamejit.  The  ends  of  the  bone  are 
smooth  and  rounded  so  as  to  move  freely  upon  each  other. 

In  some  joints  the  movements  are  simply  forward  and 
backward  like  a  hinge.  The  fingers,  toes,  elbows,  knees, 
and  ankles  are  hinge  joints. 

In  some  joints  the  movements  can  be  made  forward  and 
backward  and  sideways  like  a  ball  in  a  socket.  The 
thumbs,  great  toes,  shoulders,  and  hips  have  this  kind  of 
a  joint.  In  each  the  end  of  one  bone  is  spherical  and  fits 
into  a  hollow  socket  in  the  other. 

In  other  joints  one  bone  can  only  rotate  about  another 
as  a  pivot.  In  its  union  with  the  spine,  the  skull  turns 
about  a  fingerlike  projection  upon  the  top  of  the  second 
vertebra.  At  the  elbow,  the  upper  end  of  the  radius 
turns  in  a  socket  upon  the  side  of  the  ulna  through  half 
a  circle  of  revolution. 

654.  Structure  of  joints.  — In  all  flexible  joints  the  liga- 
ments pass  from  bone  to  bone,  like  a  collar  upon  the  out- 
side of  the  bone,  enveloping  a  cavity  which  is  lined  with 
a  thin  and  smooth  membrane,  called  synovial  membrane. 
The  synovial  membrane  secretes  a  fluid  like  the  white  of 
an  ^gg,  called  the  synovial  fluid.  The  fluid  moistens  and 
lubricates  the  joint  so  that  it  turns  smoothly  and  easily. 
If  it  is  absent  the  joint  creaks  when  moved. 

655.  Loose  joints.  —  The  two  bone  surfaces  of  each  joint  fit 
together  accurately.     There  is  a  considerable  difference  in  the  depths 


366  APPLIED    PHYSIOLOGY 

of  the  joint  sockets  and  in  the  lengths  of  the  Hgaments  in  different  per- 
sons. In  some  persons  the  sockets  are  shallow  and  the  ligaments  long, 
so  that  the  joints  can  be  bent  to  a  far  greater  degree  than  usual.  These 
persons  are  able  to  twist  and  contort  themselves  into  strange  posi- 
tions and  shapes,  and  thus  they  make  good  circus  actors. 

656.  Action  of  muscles  as  ligaments.  —  Nearly  every 
joint  is  crossed  by  muscles.  By  their  pressure  the  mus- 
cles aid  in  keeping  the  bones  in  place.  In  addition,  when 
one  muscle  acts,  those  upon  the  opposite  side  of  the  joint 
also  contract  enough  to  prevent  the  head  of  the  bone  from 
being  drawn  out  of  its  socket. 

If  all  the  muscles  and  cords  about  a  joint  are  cut,  the 
ligaments  stretch  and  the  joint  becomes  loose  and  flabby. 
If  the  ligaments  are  cut  while  the  muscles  and  cords  are 
left,  the  joint  remains  snug  and  firm. 

657.  Effects  of  pressure.  —  After  being  kept  in  an  un- 
natural position  for  some  time,  joints  tend  to  retain  the 
deformity.  In  wearing  tight  shoes,  the  great  toes  are 
bent  outward,  while  the  little  toes  are  bent  inward.  If 
the  joints  are  kept  in  this  position  day  after  day  for  years, 
they  remain  permanently  fixed  in  the  deformed  position. 
The  great  toe  joint  may  be  tender,  forming  a  bunion, 

658.  Curvature  of  the  spine.  —  The  spine  is  naturally  straight 
from  side  to  side.  Strong  muscles  aid  in  keeping  the  head  erect  and 
the  shoulders  thrown  well  back.  By  weakness  of  the  muscles  or  by 
carelessness  the  shoulders  fall  forward,  increasing  the  natural  curve  of 
the  spine  so  that  a  person  becomes  round  shouldered. 

If  a  child  habitually  sits  sidewise  at  the  desk,  leaning  continually 
upon  one  arm,  the  growing  bones  and  the  ligaments  of  the  spine  will 
gradually  become  fixed  in  the  deformed  position,  which  persists  all 
through  life.  Any  person  who,  in  his  occupation,  always  assumes  the 
same  attitude,  may  finally  be  unable  to  remove  the  curvature  from  his 
spine.  On  the  other  hand,  if  one  acquires  a  habit  of  sitting  and  walk- 
ing and  working  in  an  erect  position,  the  spine  will  grow  in  a  natural 
curve. 


JOINTS  367 

659.  Sprains. — When  a  joint  is  bent  to  a  greater  ex- 
tent than  is  natural,  the  Hgaments  and  muscles  are 
stretched  and  often  torn.  Then  there  will  be  great 
swelling  and  pain.  When  this  accident  happens,  the 
joint  should  at  once  be  put  in  water  as  hot  as  can  be 
borne,  while  more  hot  water  is  added  from  time  to  time  to 
keep  up  the  temperature  of  the  water.  The  joint  should 
have  rest  for  some  time  after  the  injury.  Recovery  is 
apt  to  be  slow. 

660.  Dislocations. — When  the  bones  of  a  joint  are 
forced  apart,  the  joint  is  dislocated,  or  out  of  joijit. 

In  a  dislocation,  the  ligaments  are  always  torn.  Then 
bleeding  will  take  place,  and  there  will  be  great  pain  and 
swelling,  while  only  slight  movements  of  the  limb  will  be 
possible. 

In  a  dislocation,  the  muscles  around  the  joint  are  irri- 
tated, and  so  contract  and  hold  the  bone  away  from  its 
socket.  Often  it  is  necessary  to  make  a  person  insensible 
with  ether  before  the  muscles  will  relax  enough  to  get  the 
joint  in  place. 

When  a  joint  is  dislocated,  the  limb  should  be  kept  as 
quiet  as  possible  by  binding  a  splint  above  and  below  the 
joint,  as  in  a  broken  bone. 

661.  Inflammation  of  joints.  —  Sometimes  the  synovial  mem- 
brane becomes  inflamed  and  pours  out  a  quantity  of  thin  fluid  which 
distends  the  joint  and  produces  great  pain.  In  rheumatism  this  often 
occurs.     Sometimes  a  blow  or  a  wrench  may  cause  it. 

Sometimes  waste  matter  of  the  body  is  deposited  in  the  synovial 
membrane  and  cartilage.  This  produces  great  pain  and  tenderness 
and  constitutes  an  attack  of  goict.  The  great  toe  joint  is  especially 
liable  to  this  disease. 

Sometimes  the  cartilage  and  ends  of  the  bone  become  distorted  and 
rough,  or  form  hard  swellings.  Then  the  limbs  cannot  be  bent  without 
producing  pain  and  a  creaking  sensation.     This  change  naturally  occurs 


368  APPLIED   PHYSIOLOGY 

in  old  persons,  and  is  due  partly  to  deposits  of  lime  in  the  cartilage  and 
partly  to  a  dry  state  of  the  synovial  membrane. 

Sometimes  a  joint  slowly  swells  and  discharges  yellow  matter  for  a 
long  time,  while  the  sufferer  gradually  loses  flesh  and  strength.  The 
disease  is  commonly  known  as  a  white  swelli?ig,  but  is  really  tuber- 
culosis, or  coiisujHption  of  the  joint.  When  it  affects  the  hip  joint,  it 
is  called  hip  joint  disease.  A  form  of  the  disease  without  the  discharge 
of  matter  may  affect  the  spine  and  produce  the  deformity  called  a 
hunchback, 

SUMMARY 

1.  The  union  of  two  bones  is  called  2i  joint. 

2.  In  joints  in  which  the  bones  do  not  move,  the  bones 

are  united  either  by  bone  or  strong  pads  of  fibrous 
tissue,  or  by  cartilage,  or  by  being  dovetailed  into 
each  other. 

3.  In  flexible  joints,  bones  are  joined  together  by  a  collar 

of  fibrous  tissue  and  by  the  action  of  muscles. 

4.  Flexible  joints  are  lined  with  synovial  membrane,  which 

secretes  a  fluid  like  the  white  of  an  ^^g  to  lubricate 
the  joint. 

5.  By    assuming    one    position    day  after   day  the   joints 

become  fixed  in  that  position. 

6.  In  sprains  and  dislocations  the  ligaments  are  stretched 

or  torn,  and  require  long  rest  in  recovery. 

7.  The    synovial   membrane    may   become   inflamed  and 

swollen. 

8.  A  joint  may  become  affected  with  tuberculosis,  forming 

a  white  sivelling  or  hip  joint  disease.  In  it  the  joint 
forms  an  abscess  and  often  discharges  matter. 

DEMONSTRATIONS 

162.  A  fowl  dressed  for  the  table  will  illustrate  the  different  kinds  of 
joints.  Notice  that  in  some  places  the  muscles  unite  with  the  ligament 
and  in  others  simply  cross  it,  usually  as  a  white  cord  or  tendon.     Cut 


JOINTS  369 

the  ligaments  half  in  two  to  show  the  cavity  of  the  joint.  Notice  the 
smooth  and  shining  appearance  of  the  synovial  membrane  which  lines 
the  joint  and  its  slight  amount  of  synovial  fluid.  Bend  the  joint  back 
and  forth  to  show  how  the  surfaces  of  the  bone  fit  into  each  other. 
Sketch  a  joint. 

163.  Notice  some  of  the  inflexible  joints.  In  an  animaPs  skull  notice 
that  the  joints  are  dovetailed  together  with  but  little  cartilage  between. 
Notice  the  tough  pads  between  the  vertebrae,  and  how  they  permit  the 
spine  to  bend  slightly.  Notice  that  the  ribs  are  united  to  the  sternum 
by  flexible  cartilage. 

164.  To  show  that  muscles  and  cords  act  as  ligaments,  clench  the 
fist  tightly.  Notice  that  the  cords  upon  the  back  of  the  hands  tighten, 
as  well  as  those  which  shut  the  hand. 

REVIEW  TOPICS 

1.  Describe  and    locate   the   inflexible   joints  with  bony 

union ;  with  union  by  cartilage ;  with  union  by  pads 
of  fibrous  tissue ;  and  with  union  by  being  dove- 
tailed together. 

2.  Describe  and  locate  hinge  joints ;  the  ball  and  socket 

joints  ;  and  the  pivot  joints. 

3.  Describe  the  structure  of  joints,  their  ligaments,  syno- 

vial membrane,  and  fluid. 

4.  Show  how  muscles  aid  the  action  of  the  ligaments. 

5.  Show  how  long-continued  pressure  affects  the  joints, 

as  in  the  great  toe. 

6.  Show  how  the  position  of  the  body  may  produce  curva- 

ture of  the  spine. 

7.  Describe  the  nature  and  treatment  of  a  sj>ram,  and  of 

a  dislocation. 

8.  Show  how  joints  may  become  inflamed. 

9.  Describe  a  white  swelling. 
10.    Describe  a  bimion. 

OV.  PHYSIOL.  —  24 


The  muscular  system. 
370 


CHAPTER  XXXIX 

MUSCLES 

662.  Movements  within  the  body.  —  Every  action  of  the 
body  has  motion  for  its  basis,  and  every  cell  possesses 
motion  of  some  form.  But  certain  cells  of  the  body  are 
set  apart  to  produce  motion  in  the  various  liquids  of  the 
body  and  to  move  different  parts  of  the  body  itself.  Cells 
whose  work  is  to  produce  motion  are  called  muscle  cells. 

663.  Involuntary  muscles.  —  Some  movements  of  the 
body  go  on  wholly  without  our  knowledge  and  are  not 
affected  by  the  will.  Such  are  the  movements  of  the 
blood,  and  of  the  peristalsis  of  the  intestine.  These  invol- 
untary movements  are  produced  by  muscle  cells  which  are 
governed  by  the  sympathetic  nervous  system.  Each  mus- 
cle cell  resembles  a  string  with  pointed  ends.  They  are 
wrapped  around  the  arteries,  intestine,  bronchi,  ?^^^ 
and  other  hollow  organs.  They  are  inter-  ^^ 
woven  with  the  other  tissues  of  the  organ  and  ^g 
cannot  be  recognized  without  a  microscope.  ^^ 

664.  Voluntary  muscles. — The  muscles  which       ^:^ 
enable  the  body  to  move  are  under  control  of       2^ 
the  will.      They  are  situated  mostly  upon  the       ^p 
outside  of  the  bones,  and  altogether  form  over       ^^ 
one  half   of  the  weight    of  the    body.       They  a  muscle  ceU 
round  out  the  figure  and  impart  to  it  strength      ^^  ^^^^' 
and  beauty.    The  other  organs  of  the  body  of  man  exist  in 
order  that  the  brain  and  muscles  may  subsist  and  work 
out  the  plans  of  man's  higher  nature. 

371 


372 


APPLIED   PHYSIOLOGY 


t 


-rl^JS^J^ 


¥ 


a 


b 


a 


Muscle  cells  cut  across 

(X  200). 
a  muscle  cell. 

b   connective  tissue  binding  the 
cells  together. 


The  lean  part  of  meat  is  muscle.     Each  muscle  can  be 

split  lengthwise  into  bundles  again  and  again  until  each 

muscle  cell  is  separated  from  the  rest.     Connective  tissue 

binds  the  whole  together. 

A   muscle    cell    is    a  cordlike   body   about  -^\-^   of   an 

inch  in  thickness.  Extending 
crosswise  upon  its  surface  are 
alternate  dark  and  light  bands 
which  serve  to  distinguish  a 
muscle  cell  from  all  other  cells  of 
the  body.  Each  cell  is  surrounded 
but  not  penetrated  by  a  network 
of  capillaries  and  is  held  in  place 
by  delicate  fibers  of  connective 
tissue,  which  are  always  small  in 
quantity  compared  with  the  cells. 
665.    Attachment  of  muscles.  —  One  end  of  a  muscular 

bundle  is  usually  attached  to  the 

periosteum  of  a  bone,  while  the 

other  end  is  joined  to  a  string  of 

connective  tissue  called  a  tendon. 

A  tendon  is  a  white  pliable  cord 

and  is  exceedingly  strong.       It 

runs    in    a    groove    lined    with 

synovial  membrane,  and  its  end 

is  usually  attached   to   a   bone. 

A     muscle     usually     forms      a 

rounded      projection     above     a 

joint    to    be    moved,    while     its 

tendons  extend  across  the  joint 

and  are  attached  to  the  perios- 
teum of  the  next  lower  bone.    This  arrangement  keeps  the 

weight  of  the  limbs  near  their  upper  extremities. 


A  thin  slice  of  a  voluntary  mus- 
cle cut  lengthwise  (X  lOO). 

a   muscle  cell. 

b   capillaries  surrounding  the  cells. 
c    connective    tissue     binding    the 
cells  together. 


MUSCLES 


373 


666.  Contraction  of  muscles.  —  When  a  muscle  cell  is 
cut  or  pinched  or  irritated  in  any  way,  it  becomes  shorter 
and  thicker.  This  is  called  a  contraction,  and  is  the  essen- 
tial peculiarity  of  muscles.  An  end  of  a  motor  nerve 
thread  touches  every  muscle  cell  and  conveys  to  it  orders 
from  the  cells  of  the  spinal  cord  and  brain.  Each  order 
causes  a  contraction. 

A  muscle  cell  requires  about  ^V  of  3-  second  to  contract  and  another 
yV  of  a  second  to  become  relaxed.  So  it  is  impossible  to  move  a  limb 
more  than  ten  times  a  second.  The  brain  sends  about  ten  orders  per 
second.  Thus  before  the  muscle  relaxes  it  receives  another  order  and 
so  remains  in  a  tremulous  state  of  contraction  which  becomes  apparent 
during  excitement  or  when  a  great  effort  is  being  made.  Each  con- 
traction is  a  change  in  the  shape  and  not  in  the  size  of  the  muscle. 


1.  II.  III. 

The  three  classes  of  levers,  and  also  the  foot  as  a  lever. 

667.  Bones  as  levers.  —  A  rigid  bar  turning  about  a 
fixed  point  or  fulcrum  is  called  a  lever.  When  the  weight 
is  at  one  end  of  the  bar  and  the  power  at  the  other  end 
while  the  fulcrum  is  between  the  two,  the  bar  is  called  a 
lever  of  the  first  class. 

When  the  weight  is  between  the  power  and  the  fulcrum, 
the  bar  is  called  a  lever  of  the  seco7id  q\2.'$>'^. 

When  the  weight  is  at  one  end,  the  fulcrum  at  the  other, 
and  the  power  between,  the  bar  is  called  a  lever  of  the 
third  class. 


374 


APPLIED    PHYSIOLOGY 


Muscle. 


Tendon 


If  the  power  is  farther  away  from  the  fulcrum  than  the 
weight,  it  will  move  a  weight  greater  than  itself,  but  if  it 

is  a  less  distance  away,  it  can  move  only 
a  weight  less  than  itself. 

A  bone  is  a  rigid  bar.  The  joint  is 
the  fulcrum  upon  which  it  turns.  The 
power  is  the  contraction  of  the  muscles 
which  are  attached  to  it.  The  weight 
is  the  weight  of  the  body  or  limb  to- 
gether with  anything  which  may  be 
grasped. 

668.  Levers  of  the  first  class  are  not 
numerous  in  the  body.  The  foot  when 
pressing  down  with  the  toes,  and  the 
head  when  it  is  raised,  are  two  examples. 

669.  Levers  of  the  second  class  are 
also  few.  The  best  example  is  the  foot 
when  standing  on  the  toes.  The  power 
is  attached  to  the  heels  and  is  furnished 
by  the  muscles  upon  the  back  side  of 
the  leg  below  the  knee.  They  end  in  a 
very  strong  tendon  called  the  tendon  of 
Achilles,  which  can  be  felt  under  the 
skin  above  the  heel.  It  is  the  largest 
tendon  in  the  body. 

670.  Levers  of  the  third  class  are 
the  most  numerous.  The  foot  in  rais- 
ing a  weight  upon  the  toes  is  an  example.  In  nearly 
all  joints  of  the  arms  and  legs  the  power  is  furnished 
by  the  muscle  attached  to  a  bone  near  the  fulcrum 
or  joint,  while  the  weight  is  farther  away  or  near  the 
outer  extremity  of  the  bone.  Most  of  these  muscles  are 
so  attached  to  their  bones  that  they  must  exert  a  force 


Right  forearm. 


MUSCLES  375 

greater  than  the  weight  which  they  move.  But  the  outer 
end  of  a  lever  moves  over  a  greater  distance  in  a  given 
time  than  the  part  near  the  fulcrum.  So  if  a  muscle 
loses  power  by  its  attachment  to  a  bone,  it  gains  in  rapidity 
of  motion.  The  muscles  of  the  body  are  strong  enough  to 
combine  strength  with  quickness  of  motion. 

The  joints  of  the  arms  and  legs  are  mostly  so  arranged  that  the  limb 
can  form  a  straight  line,  but  can  be  bent  in  only  one  direction.  The 
muscles  which  bend  a  limb  are  called  the  flexors,  while  those  which 
straighten  it  are  called  extensois.  Flexor  and  extensor  muscles  are 
usually  arranged  in  opposing  pairs,  with  the  flexors  upon  the  front  and 
the  extensors  upon  the  back  side  of  the  limb.  The  flexor  of  the  elbow 
reaches  from  the  elbow  to  the  shoulder  upon  the  front  of  the  arm  and 
is  called  the  biceps.  The  extensor  of  the  elbow  extends  in  the  same 
way  upon  the  back  of  the  arm  and  is  called  the  triceps.  Both  the  flexors 
and  extensors  of  the  wrist  and  fingers  are  situated  between  the  elbow 
and  the  wrist.     Only  a  few  small  ones  are  in  the  hand. 

The  muscles  which  flex  the  knee  end  in  strong  tendons  which  can 
be  felt  as  the  hamstrings  upon  the  back  of  the  joint.  The  muscles 
which  extend  the  knee  end  in  a  single  large  tendon  inside  of  which  is 
the  patella.  The  patella  acts  as  a  pulley  to  protect  the  joint  from  the 
action  of  the  tendon. 

The  muscles  of  the  ankles  and  toes  are  arranged  much  like  those  of 
the  wrist  and  fingers.  By  practice  while  young,  it  is  possible  to  learn 
to  use  the  toes  in  the  same  way  as  the  fingers. 

671.  Back  muscles.  — The  backbone  is  held  upright  and 
bent  backward  by  large  muscles  which  form  ridges  upon 
each  side  of  the  spine.  They  stretch  the  whole  length  of 
the  spine  so  that  the  weight  and  power  are  at  the  same 
place  while  the  fulcrum  is  the  point  of  bending.  Thus  the 
spine  is  equivalent  to  a  lever  of  the  second  or  third  class 
which  uses  most  of  the  power  of  the  muscle.  So  the  back 
possesses  great  power  with  slow  motion. 

672.  Standing  is  done  by  the  contraction  of  the  opposing  flexor 
and  extensor  muscles  of  the  lower  part  of  the   body,  so  that  the 


3/6  APPLIED   PHYSIOLOGY 

spine  and  legs  are  held  rigid.  If  one  set  overacts,  it  pulls  the  body  to 
one  side  and  tends  to  upset  it.  Then  the  opposing  set  contracts  and 
rights  the  body.  In  standing,  the  two  sets  continually  act  in  this  way. 
Walking  is  due  to  a  regular  action  of  the  flexor  and  extensor  muscles 
of  the  leg,  in  such  a  way  that  there  is  always  one  foot  upon  the  ground. 
In  running,  the  whole  body  is  completely  removed  from  the  ground 
at  every  step. 

673.  Face  muscles.  —  The  expression  of  the  face  is  due 
to  flat  muscles  which  are  attached  to  the  skin.  A  circular 
muscle  surrounds  the  mouth  and  each  eye,  while  other 
muscles  radiate  from  their  edges.      The   contractions  of 


Illustration  of  the  change  of  expression  produced  by  the  muscles 
of  the  mouth. 

these  muscles  cause  the  mouth  and  eyes  to  assume  a  great 
variety  of  positions.  Even  the  nose  may  be  moved  by 
muscles,  and  in  rare  cases  the  ears  also.  The  different 
shapes  of  the  mouth  and  eyes  which  these  muscles  produce 
are  reliable  indications  of  the  feelings  of  the  mind. 

674.  Muscular  power.  —  The  power  which  the  muscles 
use  is  derived  from  the  oxidation  both  of  food  and  of  their 
own  substance.  In  their  work  they  use  about  one  fourth 
of  the  total  heat  produced  in  the  body. 

A  horse  can  drag  about  two  thirds  of  its  own  weight,  while  an  ant 
can  drag  40  times  its  own  weight,  and  a  grasshopper  can  leap  300  times 
its  own  length.  In  proportion  to  their  size,  all  insects  seem  to  be  far 
stronger  than  man.     The  strength  of  a  muscle  depends  upon  its  thick- 


MUSCLES  377 

ness  and  not  upon  its  length,  yet  in  animals  the  muscle  must  be  made 
many  times  longer  than  in  insects  as  well  as  thicker.  Thus  the  muscles 
of  animals  have  more  weight  to  lift  and  do  a  greater  amount  of  work  in 
proportion  to  their  size.  A  man's  muscle  fiber  is  really  the  strongest 
known.  An  insect  made  as  large  as  a  man  would  probably  be  unable 
to  move  a  limb. 

675.  Precision  of  movement.  —  By  means  of  the  muscular 
sense  it  is  possible  to  regulate  the  action  of  a  muscle  with 
great  precision.  But  as  the  effort  put  forth  is  greater,  the 
ability^  to  regulate  it  is  less.  So  while  slow  and  delicate 
movements  can  be  made  with  precision,  rapid  and  power- 
ful motions  are  less  under  control.  After  a  muscle  has 
exerted  itself  to  its  full  capacity,  it  is  unable  to  perform 
delicate  movements  with  precision  for  some  time. 

676.  Alcohol  and  muscle.  —  Strong  drink  in  any  form  dimin- 
ishes both  the  strength  and  the  endurance  of  muscles.  Soldiers  and 
athletes  are  not  allowed  to  use  it  during  periods  of  great  exertion.  It 
also  interferes  with  the  precision  of  movements.  Drinkers  are  not 
allowed  to  work  at  railroading,  where  quickness  and  precision  of  move- 
ments are  always  required.  Tobacco  also  weakens  the  muscles  and 
lessens  their  precision  of  movement. 

677.  Physical  effects  of  exercise.  —  When  used,  most 
cells  of  the  body  take  in  more  nourishment,  and  increase 
in  size  and  strength.  Muscles,  especially,  grow  larger  and 
stronger  by  use.  Then  the  digestion,  circulation,  and 
respiration  all  show  increased  vigor  to  supply  them  with 
extra  energ}^     Thus  the  whole  body  grows  stronger. 

Round  shoulders  are  most  often  due,  not  to  weakness  of  the  spine, 
but  to  weakness  and  inaction  of  the  muscles  of  the  back.  The  remedy 
is  not  to  apply  braces,  for  that  only  permits  the  muscles  to  rest  and  be- 
come weaker,  but  to  make  constant  efforts  to  throw  the  shoulders  back 
and  so  to  increase  the  strength  of  the  muscles.  Military  drill  makes 
soldiers  erect  for  this  reason. 

678.  Overwork.  —  If  the  muscles  turn  too  much  heat 
of  the  body  to  motion  and  work,  there   is  too   little  left 


378  APPLIED    PHYSIOLOGY 

to  carry  on  the  actions  of  the  internal  organs.  Then 
there  will  be  less  food  prepared  for  the  repair  of  the  cells, 
and  to  replenish  the  fuel  for  oxidation.  So  the  whole 
body,  including  the  brain,  will  remain  fatigued.  Besides 
the  energy  expended  by  the  muscles,  the  brain  also  does  a 
large  amount  of  work  in  sending  orders  for  their  work. 
Probably  the  nervous  system  always  becomes  fatigued 
before  the  muscles. 

679.  Kinds  of  exercise.  —  It  is  a  problem  for  students 
and  clerks  to  determine  how  much  exercise  will  rest  and 
stimulate  the  brain  to  the  greatest  degree,  and  yet  take 
no  energy  from  it.  The  kind  which  a  person  enjoys  best 
is  the  best  exercise  for  that  person.  If  possible,  the  exer- 
cise should  be  of  a  form  which  will  turn  one's  thoughts 
completely  from  the  day's  work  and  from  the  exercise 
itself.  So  a  useful  occupation  or  some  absorbing  game  is 
especially  valuable  as  exercise.  Dumb  bells,  chest  weights, 
and  all  kinds  of  gymnastic  exercises  are  excellent  for 
developing  the  muscles.  Their  only  disadvantage  is  that 
their  use  becomes  monotonous,  and  a  person  must  force 
himself  to  use  them.  They  have  the  advantage  that  they 
can  be  exactly  regulated  to  develop  any  defective  part  of 
the  body.  When  done  in  classes  and  under  an  instructor 
they  are  especially  valuable. 

680.  Amount  of  exercise.  —  A  few  moments  of  brisk 
running  or  romping  will  set  the  blood  flowing  faster  and 
produce  a  clearer  brain  than  an  hour  of  slow  walking.  A 
person's  own  feelings  should  warn  him  when  to  stop. 
Boys  and  girls  need  plenty  of  exercise  toward  the  end  of 
their  time  of  growth.  A  body  well  developed  by  exercise 
carries  its  strength  through  life. 

In  a  school,  a  position  upon  either  the  baseball  or  football  or  athletic 
team  often  uses  the  surplus  energy  which  in  former  years  was  expended 


MUSCLES  379 

in  midnight  hazings,  and  also  develops  the  traits  of  bravery,  manliness, 
and  self-reliance.  There  is  a  special  danger  of  overexertion  in  com- 
petitive sports,  but  with  intelligent  oversight  of  the  teachers  they  are  a 
great  benefit  to  all. 

SUMMARY 

1.  Cells   whose   use    is   to    produce   motion    are    called 

muscle  cells. 

2.  In  the  arteries  and  in  most  of  the  organs  of  the  chest 

and  abdomen  are  spindle-shaped  muscle  cells,  which 
are  not  affected  by  the  will,  but  are  controlled  by 
the  sympathetic  system. 

3.  Muscles   covering  the   bones   and   moving  the  body 

under  the  control  of  the  will  form  one  half  of  the 
body. 

4.  Voluntary  muscles  are  made  of  ribbonlike  cells  which 

are  marked  crosswise. 

5.  Impulses  from  motor  nerves   cause  a  muscle  to  be- 

come thicker  and  shorter,  so  that  it  moves  any- 
thing attached  to  its  end. 

6.  A  muscle  ends  in  a  stringlike  tendon  which  crosses  a 

joint,  and  is  attached  to  the  lower  of  the  two  bones 
which  form  the  joint: 

7.  Muscles  are  arranged  in  pairs.     Those  upon  the  back 

side  of  a  limb  usually  straighten  the  joint,  while 
those  upon  the  front  side  bend  it. 

8.  Owing  to  the  rhanner  of  their  attachment,  most  muscles 

must  put  forth  far  greater  force  than  the  weight 
which  they  can  lift. 

9.  A  piece  of  a  man's  muscle  is  stronger  than  any  other 

muscle  of  the  same  size. 
10.    The  power  for  contraction  of  a  muscle  is  derived  from 
the  heat  of  oxidation  within  the  body.     About  one 
fourth  of  the  heat  is  thus  used. 


380  APPLIED   PHYSIOLOGY 

11.  By  exercise  of  the  muscles,  the  nutrition  of  the  whole 

body  is  improved. 

12.  Too  much  exercise  uses  the  power  which  should  go 

to  the  brain  and  other  organs  and  so  harms  the 
body. 

13.  That   form   of   exercise   is   usually   best  which  most 

interests  a  person. 

DEMONSTRATIONS 

165.  Skin  a  chicken's  leg  and  separate  each  muscle.  Show  their 
broad  upper  attachments  and  the  small  tendons  into  which  the  lower 
ends  taper.  Cut  off  the  skin  from  the  lower  parts  of  the  legs  and  toes 
and  show  how  the  tendons  are  attached  to  the  toes.  Notice  that  bend- 
ing the  leg  tightens  the  tendons  and  flexes  the  toes.  Explain  how  this 
compels  the  toes  to  grasp  the  perch  while  the  fowl  is  roosting.  Pick  a 
muscle  apart  to  show  the  separate  fibers.     Sketch  a  muscle. 

166.  Point  out  the  main  groups  of  muscles  upon  a  boy.  Have  him 
perform  such  motions  as  raising  his  arm  and  clenching  his  fist,  and  feel 
what  muscles  are  in  action.  Notice  that  when  one  set  of  muscles  is  in 
action  the  opposing  set  also  acts  so  as  to  steady  the  limb.  Point  out 
the  tendons,  especially  in  the  wrist  and  knee. 

167.  With  two  needles  tear  apart  a  small  shred  of  muscle  from  a 
piece  of  cooked  meat  and  examine  it  under  the  microscope  with  a  power 
of  at  least  200  diameters.  Sketch  the  ribbonlike  muscle  cells  and  their 
fine  cross  markings.  Notice  the  small  amount  of  wavy  connective 
tissue  between  the  cells.  Examine  a  prepared  specimen  to  show  the 
cells  cut  across  and  the  capillaries  surrounding  the  cells. 

168.  Show  involuntary  muscle  cells  by  preparing  a  shred  from  a 
fowl's  gizzard,  as  in  demonstration  167.     Sketch  the  specimen. 

169.  Hold  a  pencil  firmly  with  the  elbow  flexed.  Contract  all  the 
muscles  of  the  arm  strongly.  Notice  that  the  whole  arm  trembles. 
Now  let  the  pencil  tap  the  table  by  means  of  this  trembling  motion,  and 
notice  that  the  taps  are  about  ten  a  second.  Explain  that  the  taps  are 
due  to  successive  motor  impulses  from  the  brain.  Now  tap  the  table 
rapidly  with  the  ordinary  motion  of  the  hand.  Notice  that  it  can  be 
done  only  about  five  or  six  times  a  second.  Explain  that  in  this  case  the 
mind  must  cause  two  separate  sets  of  muscles  to  contract  alternately. 


MUSCLES  381 

REVIEW  TOPICS 

1.  Show  that  motion  is  essential  to  the  process  of  life. 

2.  Describe  involuntary  muscles  and  tell  their  use. 

3.  Describe  how  voluntary  muscles  appear  to  the  naked 

eye  and  under  the  microscope. 

4.  Describe  tendons;    how  they  cross   the  joints;    and 

their  attachment  to  bones. 

5.  Describe  the  contraction  of  a  muscle. 

6.  Describe  the  three  kinds  of  levers ;  show  how  bones 

and  m.uscles  form  levers ;  and  give  examples  of  each 
kind. 

7.  Describe  the  arrangement  of  muscles  in  opposing  sets. 

8.  Describe  the  action  of  muscles  at  the  elbow ;  at  the 

wrist ;  at  the  fingers  ;  at  the  hip  ;  at  the  knee  ;  at 
the  ankle  ;  at  the  toes  ;  in  the  back ;  over  the  abdo- 
men ;  and  upon  the  face. 

9.  Show  how  standing  is  performed ;    how  walking ;  and 

how  running. 

10.  Give  the  source  and  amount  of  muscular  power. 

11.  Show   that   great  exertion   impairs   the  precision   of 

movements. 

12.  Show  that  muscle  training  is  really  mind  training. 

13.  Show  that  physical  exercise  benefits  the  whole  body; 

and  that  overwork  fatigues  the  brain. 

14.  Show  what  kind  of  exercise  is  the  best. 

15.  Show  how  to  regulate  the  amount  of  exercise. 

16.  Give  an  estimate  of  the  value  of  competitive  sports  in 

schools. 


CHAPTER   XL 

BACTERIA  AND   DISEASE 

681.  Dangers  to  life.  —  Man's  health  is  often  assailed 
by  his  inward  appetites  and  desires.  He  is  also  exposed 
to  accidents  and  dangers  from  without.  Formerly  men 
were  in  constant  danger  from  wild  animals,  but  now  man  — 
the  noblest  and  most  powerful  living  being  —  is  constantly 
assailed  and  often  conquered  by  the  smallest  and  simplest 
of  living  creatures.  In  the  midst  of  his  work  he  may  be 
stricken  with  a  deadly  disease  because  millions  of  tiny 
creatures  are  poisoning  the  cells  of  his  body. 

The  microscope  has  revealed  a  world  of  tiny  creatures  of 
an  infinite  variety  of  form  and  manner  of  life.  Three  of 
the  simplest  forms  are  yeasty  mold,  and  bacteria.  All  of 
them  are  of  importance  to  man. 

682.  Yeast  is  a  plant  which  consists  of  a  single  cell 
scarcely  larger  than  a  red  blood  cell.  The  cells  live  upon 
sugar,  and  begin  a  series  of  changes  to  return  it  to  the  air 
and  water  for  use  as  plant  food.  Were  it  not  for  this 
provision,  much  plant  food  might  encumber  the  earth  in 
the  form  of  sugar  and  starch,  and  both  man  and  animals 
might  starve.  After  the  sugar  upon  which  yeast  cells  feed 
is  used  up,  they  remain  in  a  dormant  state,  and  some  be- 
come dried  and  pass  off  as  dust.  Some  are  always  float- 
ing about  in  the  air  ready  to  grow  in  anything  containing 
sugar.  Yeast  must  have  warmth  and  moisture  for  its 
growth.     So  cold  or  dried  fruit  does  not  sour.     Yeast  is 

382 


BACTERIA  AND   DISEASE 


383 


used  in  bread  making  and  in  the  manufacture  of  alcohol 
(see  Chapter  IV). 

683.  Molds  form  a  class  of  plants  which  may  grow  in 
nearly  all  kinds  of  moist  substances,  and  there  induce  a 
kind  of  decay.  They  may  usually  be  recognized  by  their 
furry  growth  on  the   surface  of  the  affected  substance. 


Diagram  of  mold  ( x  200). 

a  ball  of  spores  above  the  surface. 
d   threads  beneath  the  surface. 
c    spores  beneath  the  surface. 

The  plants  themselves  are  usually  a  series  of  threads  which 
burrow  beneath  the  surface.  At  intervals  they  send  up 
slender  shoots  which  bear  germ  cells  or  spores.  These 
shoots  constitute  the  fur  which  is  usually  called  mold,  but 
many  kinds  form  their  spores  beneath  the  surface.  The 
spores  are  microscopic  in  size,  and  can  float  in  the  air  and 
grow  into  mold  plants  when  they  fall  upon  a  suitable  soil. 
Most  forms  grow  only  on  dead  material,  but  a  few  can 
grow  on  living  matter.  The  smut  and  rust  on  grain  and 
fruit  are  plants  similar  to  molds.     Ringworm  is  due  to  a 


384  APPLIED   PHYSIOLOGY 

mold  which  grows  in  the  human  skin.  Mildew  and  toad- 
stools belong  to  the  same  family  as  molds.  In  nature 
molds  disintegrate,  and  return  to  the  soil  and  air  all  kinds 
of  dead  plant  and  animal  substances,  especially  hard  and 
resisting  tissues  like  bones,  tree  trunks,  and  skins,  so  that 
they  can  again  become  available  as  plant  food.  In  warm, 
humid  weather  molds  grow  readily  and  are  often  destruc- 
tive to  food  and  clothing. 

684.  Bacteria.  —  The  smallest  and  simplest,  as  well  as 
the  most  numerous  of  living  creatures,  are  round  or  rod- 
shaped  bodies  from  g^To  ^°  ToToTi  ^^  ^^  ^^^^  ^^  breadth, 
and  seldom  more  than  i-^qq  of  an  inch  in  length.  They 
are  sometimes  called  microbes^  but  more  common  names 
are  bacteria  or  germs.  They  are  all  plants  whose  mode  of 
growth  somewhat  resembles  the  yeasts  and  molds.  Like 
yeast  and  mold  they,  or  their  spores,  are  scattered  every- 
where in  the  air.  When  they  fall  upon  moist  albumin  they 
grow.  A  single  one  can  produce  over  10,000,000  in  the 
course  of  twenty-four  hours.  They  often  resist  influences 
which  would  destroy  most  other  forms  of  life.  Even  boiling 
for  five  minutes  fails  to  destroy  the  spores  of  some. 

685.  Effects  of  bacteria.  —  Bacteria  destroy  the  substances 
in  which  they  grow.  Most  forms  of  decay  are  due  to  the 
action  of  certain  varieties  of  bacteria.  They  cause  dead 
matter  to  become  soft  and  melt  away,  usually  with  the 
production  of  foul-smelling  gases  and  a  variety  of  poison- 
ous ptomaines.  In  the  soil  there  are  forms  of  bacteria 
which  oxidize  all  kinds  of  animal  and  vegetable  albumin 
as  thoroughly  as  though  it  were  burned.  Thus  bacteria 
destroy  the  dead  and  waste  matter  of  vegetables  and  ani- 
mals and  prepare  it  for  vegetable  food  again.  Yeast,  mold, 
and  bacteria  are  indispensable  friends  of  all  living  beings ; 
and  decay  is  a  step  in  the  preparation  of  our  food. 


BACTERIA  AND  DISEASE 


385 


Bacteria  growing  in  the  mouth  (x  400). 

The  specimen  was  obtained  by  scraping  a 

healthy  mouth. 

a  nucleus  of  an  epithelial  cell. 

b  different  forms  of  bacteria. 

c  outline  of  an  epithelial  cell. 


686.  Effects  of  bacteria  upon  living  bodies.  —  Wherever 
there  is  a  moist  cavity  containing  albumin,  bacteria  may 
grow.  The  mouth  is 
usually  swarming  with 
them,  and  may  be  offen- 
sive from  the  decay 
which  they  cause.  They 
also  grow  abundantly  in 
the  intestine.  A  few 
forms  can  grow  in  the 
lymph  spaces  within  a 
living  body.  Their  poi- 
sons, circulating  with  the 
blood,  may  produce  vari- 
ous diseases.  Erysipe- 
las, diphtheria,  typhoid 
fever,  consumption,  cholera,  lockjaw,  and  the  grippe  are  all 
caused  by  living  germs  which  enter  the  circulation  from 
without.     Because   these  diseases  are   always   caused  by 

an  influence  from  outside 
they  are  said  to  be  i7ifec- 
tious. 

Measles,  scarlet  fever, 
mumps,  whooping  cough, 
and  smallpox  also  are  due 
to  some  influence  from 
without  the  body.  This 
influence  is  supposed  to 
proceed  from  a  kind 
of  germ,  also.  These 
diseases  can  be  caught 
by  being  in  the  same 
room  with  a  sick  person,  and  so  are  said  to  be  cofitagious. 

OV.  PHYSIOL.  —  25 


Bacteria  growing  in  a  kidney  and  producing 
an  abscess  (X  300). 
a   kidney  tube. 

b   white  blood  cell  attacking  bacteria. 
c   bacteria. 
d  blood  tube  of  the  kidney. 


386  APPLIED   PHYSIOLOGY 

687.  How  bacteria  enter  the  body.  —  Germs  of  an  infec- 
tious disease  can  grow  outside  the  body  in  a  damp  soil 
containing  animal  or  vegetable  matter.  They  may  grow 
in  damp  clothing,  or  in  sinks  or  wells,  or  in  the  soil,  and 
may  cause  disease  in  whoever  happens  to  take  them  into 
the  body.  Dirt  and  filth  make  good  soil  for  the  growth  of 
the  germs,  and  are  well-known  causes  of  disease.  The 
germs  may  become  dry  and  remain  in  a  dormant  state  for 
years,  and  finally  produce  the  disease  again. 

Bacteria  may  enter  the  body  wherever  the  epithelium  is  gone,  and 
the  lymph  spaces  are  bare.  Even  a  scratch  or  a  pin  prick  may  admit 
thousands  at  one  time.  They  can  also  enter  through  the  mucous  mem- 
brane of  the  nose  or  throat,  or  they  may  be  swallowed  in  drinking 
water  or  licked  off  from  a  knife  or  spoon  which  another  person  has  used. 

688.  How  the  body  destroys  bacteria.  —  Germs  of  disease 
constantly  surround  us,  and  the  skin  is  constantly  being 
scratched  and  pricked,  affording  them  entrance.  Yet  only 
in  rare  instances  do  they  grow  and  produce  sickness,  for 
the  body  has  three  very  ef^cient  weapons  of  defense. 

First.  The  white  blood  cells  have  a  special  power  of 
seeking  out  bacteria  and  the  toxins  which  they  produce, 
and  of  enveloping  and  destroying  them. 

Second.  TJie  plasma  of  the  blood  and  lymph,  by  some 
chemical  power,  is  able  to  destroy  germs  of  disease. 

Third.  The  serum  of  the  blood  often  contains  a  sub- 
stance called  an  antitoxin,  which,  while  it  may  be  a  poison 
itself,  also  poisons  the  germs  and  §o  stops  their  action. 
When  a  disease  has  progressed  for  a  few  days  or  weeks, 
the  antitoxin  is  formed  in  sufficient  amount  to  poison  the 
germs,  and  so  the  disease  comes  to  an  end. 

If  the  toxins  of  diphtheria  germs  grown  outside  the  body  are  injected 
into  a  horse,  the  plasma  of  its  blood  will  contain  the  antitoxin  of  the 
disease.     If  its  blood  is  drawn  and  allowed  to  clot,  the  clear  serum  will 


BACTERIA  AND   DISEASE  387 

contain  the  antitoxin,  and  if  injected  into  a  man  suffering  with  diphthe- 
ria, will  tend  to  overcome  the  germs  and  to  cure  the  disease. 

Cows  sometimes  have  a  disease  which  seems  to  be  a  modified  form 
of  smallpox.  By  vaccination,  the  same  disease  can  be  transmitted  to  a 
man  in  whom  it  causes  but  slight  inconvenience,  but  yet  protects  him 
against  smallpox  almost  as  thoroughly  as  an  attack  of  the  disease  it- 
self. Universal  vaccination  has  destroyed  the  terrors  of  smallpox,  so 
that  from  being  one  of  the  most  common  and  deadly  of  diseases  it  is 
now  one  of  the  rarest. 

689.  Destruction  of  germs  outside  the  body.  —  The  sun  is 

one  of  the  most  efficient  agents  in  destroying  bacteria  of  disease.  It 
acts  partly  by  drying  the  food  upon  which  they  live  and  partly  by 
means  of  its  own  chemical  power.  An  abundance  of  sunshine  in  a 
place  renders  it  almost  surely  free  from  disease.  In  some  hot  and  dry 
climates  decay  is  almost  unknown,  for  bodies  become  dried  before 
the  germs  can  grow.  On  the  other  hand,  darkness,  decay,  and  disease 
go  together. 

The  w/;/^  drives  away  the  germs.  In  the  open  air  it  is  almost  im- 
possible to  transmit  disease.  In  closed  rooms,  germs  which  are  given 
off  from  a  diseased  body  may  collect  in  great  numbers,  and  in  sick 
rooms  may  reenter  the  sick  person  and  so  prolong  his  sickness.  Rim- 
ning  water  also  removes  the  germs. 

The  soil  destroys  germs  of  disease.  In  it  are  special  germs  whose 
work  is  to  oxidize  all  organic  matter,  including  other  kinds  of  germs. 
It  also  filters  out  the  germs  so  that  they  can  spread  only  a  few  feet,  un- 
less the  ground  is  continuously  soaked  with  germ-laden  sewage. 

690.  Antiseptics.  —  Man  uses  three  principal  means  to 
destroy  disease  germs  which  may  threaten  him.  In  the 
first  place,  he  may  wash  them  away  with  soap  and  water. 
He  can  thus  get  rid  of  most  germs. 

Secondly.  A  boiling  heat  applied  for  fifteen  minutes 
will  kill  all  kinds  of  germs.  A  substance  freed  from 
germs  is  said  to  be  sterilized.  Clothes  and  utensils  used 
in  a  sick  room  can  be  made  safe  for  future  use  by  boiling. 
Before  a  surgical  operation,  the  instruments  and  dressings 
are  thoroughly  sterilized  by  boiling. 


388  APPLIED   PHYSIOLOGY 

Thirdly.  A  variety  of  chemical  substances  called  anti- 
septics are  poisonous  to  bacteria  and  destroy  them  almost 
at  once.  Carbolic  acid  added  to  from  twenty  to  one  hun- 
dred times  its  weight  of  water  is  very  efficient  in  destroy- 
ing germs  which  it  can  touch.  Bichloride  of  mercury 
added  to  from  one  thousand  to  five  thousand  times  as 
much  water,  is  also  very  good,  but  it  destroys  iron  or  tin 
vessels.     Chloride  of  lime  is  also  much  used. 

Substances  must  come  into  intimate  contact  with  germs  in  order  to 
kill  them.  A  little  carbolic  acid  or  other  antiseptic  may  impart  an 
odor  to  a  room  or  overcome  a  smell,  but  to  destroy  the  germs  it  must 
be  applied  in  quantity  directly  to  the  germ. 

Before  a  surgical  operation  the  surgeon  washes  and  sterilizes  his 
hands,  and  covers  his  clothes  with  a  sterilized  gown.  He  carefully 
avoids  touching  any  object  which  has  not  been  sterilized  either  by  heat 
or  by  chemicals.  Before  he  operates  he  scrubs  and  sterilizes  the  field 
of  operation  just  as  he  did  his  hands,  and  then  surrounds  it  with  steril- 
ized towels.  At  the  end  of  the  operation  he  covers  the  wound  with  a 
dressing  which  has  been  sterilized  by  heat  or  chemicals.  Then  no 
germs  can  enter,  and  the  largest  wounds  heal  in  a  few  days  without 
pain  or  discharge.  The  safety  of  operations  now  as  compared  with 
those  of  twenty  years  ago  lies  in  the  discovery  of  how  to  exclude  germs 
of  disease. 

691.  Care  of  a  sick  room. — When  a  person  is  sick,  every 
effort  should  be  made  to  exclude  germs  of  sickness.  Fresh  air  and 
sunshine  are  always  of  the  utmost  importance  in  a  sick  room.  It  will 
always  be  better  to  run  the  risk  of  having  the  room  a  little  cold  than  to 
have  its  air  close. 

In  contagious  and  infectious  diseases,  air  and  sunlight  are  the  chief 
means  of  destroying  the  germs. 

Clea7iliness  should  always  be  enforced  in  a  sick  room.  The  night 
clothes  and  bed  linen  should  be  changed  as  often  as  they  are  soiled. 
The  whole  body  should  be  bathed  daily,  and  the  teeth  and  mouth 
cleansed. 

Talking  above  all  things  disturbs  a  patient.  Especially  avoid  all 
references  to  doleful  cases  of  suffering  like  the  patient^s.     Do  not  ask 


BACTERIA   AND   DISEASE  389 

him  if  he  will  have  this  thing  or  that,  but  bring  it  to  him  without 
annoying  him  with  the  necessity  of  deciding  for  you.  Do  not  argue 
with  the  patient,  but  kindly  agree  with  him.  Be  good  tempered  and 
always  thoughtful  of  his  welfare. 

In  a  contagious  disease  all  visitors  should  be  excluded  from  the  room, 
and  all  furniture  not  absolutely  necessary  should  be  removed. 

When  the  disease  is  at  an  end,  the  sick  room  should  be  thoroughly 
scrubbed  with  an  antiseptic.  It  should  be  opened  to  the  sunlight  and 
air  for  several  weeks  before  being  used  again.  Everything  possible  in 
the  room  should  be  boiled  or  scrubbed.  The  patient  should  receive  a 
thorough  bath  before  leaving  the  sick  room. 

692.  Blood  poisoning.  —  Disease  germs  may  grow  upon 
any  open  wound,  making  it  tender  and  causing  it  to  run 
matter.  In  severe  forms  they  cause  a  swelling  of  the  sur- 
rounding parts,  producing  erysipelas  or  blood  poisoning. 
All  this  can  be  prevented  or  overcome  by  applying  clean 
or  antiseptic  dressings. 

Milk,  in  summer  time,  forms  a  good  soil  in  which  germs 
from  the  air  grow  and  form  acids  and  other  poisons. 
They  produce  stomach  and  intestinal  disease  in  bottle-fed 
babies.  Boiling  the  milk  and  bottles  destroys  the  bacteria 
and  prevents  the  disease. 

Consumption  or  tuberculosis,  is  the  germ  disease  most 
to  be  feared.  Its  germs  will  grow  in  any  tissue  of  the 
body  and  there  produce  tiny  nodules  like  pinheads.  After 
a  while  these  nodules  break  down  and  form  abscesses. 
They  are  found  most  often  in  the  lungs. 

The  disease  spreads  mainly  by  means  of  the  germs 
given  off  from  the  mouth.  Becoming  dried,  they  float  in 
the  air.  So  all  secretions  from  the  mouth  should  be  col- 
lected and  destroyed. 

693.  Boards  of  health.  —  In  every  community  the  law  estab- 
lishes boards  of  health,  whose  duty  it  is  to  see  that  cases  of  conta- 
gious diseases  are  properly  isolated ;   to  see  that  no  premises  become 


390  APPLIED   PHYSIOLOGY 

filthy,  and  that  no  diseases  are  brought  into  the  country  from  foreign 
lands.  Owing  to  the  strictness  and  efficiency  of  these  boards,  conta- 
gious diseases  are  now  as  rare  and  harmless  as  they  were  once  common 
and  deadly. 

SUMMARY 

1.  Yeast  is  composed  of  living  plants  which  begin  the  work 

of  returning  sugar  back  to  its  original  elements. 

2.  Mold  is  composed  of  tiny  rodlike  plants  which  grow 

through  animal  and  vegetable  tissues  and  destroy 
their  albumin. 

3.  Bacteria  are  the  smallest  living  beings.     They  cause 

decay  and  change  albumin  back  to  its  elements  in 
the  air  and  soil. 

4.  Bacteria  may  produce  virulent  poisons. 

5.  A  few  kinds  of  bacteria  grow  in  the  body  and  there 

produce  various  forms  of  disease,  some  of  which 
can  be  transmitted  to  other  persons. 

6.  The  body  is  protected  against  the  bacteria  of  disease 

by  the  white  blood  cells,  by  the  plasma,  and  by  sub- 
stances produced  in  the  blood. 

7.  Outside  of  the  body,  sunlight,  fresh  air,  running  water, 

and  the  soil  destroy  disease  germs. 

8.  Man  destroys  disease  germs  by  washing  them  away, 

by  boiling  objects  containing  them,  and  by  poison- 
ing them  with  such  substances  as  carbolic  acid  and 
bichloride  of  mercury. 

9.  Sunlight,  fresh  air,  and  cleanliness  are  essentials  in 

every  sick  room,  and  especially  in  infectious  diseases. 

10.  After  an  infectious  disease,  the  room  and  all  its  con- 
tents should  be  scrubbed,  and  thoroughly  aired  for 
a  month. 

1.1.  The  law  organizes  boards  of  health  to  control  infec- 
tious diseases  and  their  causes. 


BACTERIA  AND  DISEASE  39 1 


DEMONSTRATIONS 

170.  Place  a  little  yeast  upon  a  microscope  slide  and  examine  it 
with  a  power  of  at  least  200  diameters.  Notice  the  oval  cells  from 
which  smaller  cells  are  budding. 

171.  Take  a  bit  of  mold  from  cheese  or  bread  and  examine  it  with  a 
power  of  at  least  200  diameters.  Notice  the  strings  of  mold  which 
appear  like  very  small  jointed  rods.  Notice  the  collections  of  round 
spores  at  the  tops  of  the  projecting  stalks. 

172.  Place  a  little  hay  in  a  bottle  of  water  and  set  it  in  the  sun. 
After  a  few  days,  place  a  drop  of  the  water  upon  a  glass  slide  and 
examine  it  with  a  power  of  at  least  400  diameters.  Notice  that 
numerous  bodies  of  various  sizes  and  shapes  are  swimming  in  the 
drop.  These  are  the  animalculcB  which  older  books  describe.  Notice 
also  the  real  bacteria  which  appear  as  the  finest  kinds  of  dots  and  short 
lines.  Most  of  them  are  in  constant  motion.  Only  a  few  kinds  of 
bacteria  can  be  recognized  by  their  appearance. 

173.  Prepare  some  gelatine  as  if  for  the  table,  and  pour  some 
while  hot  into  a  tightly  covered  dish  which  has  been  boiled.  Take  oiF 
the  cover  for  a  moment  before  the  class,  and,  replacing  it,  set  the  dish 
aside  for  a  few  days.  Then  a  few  specks  of  mold  or  of  scum  will  appear 
upon  the  surface,  each  showing  where  a  germ  has  fallen  from  the  air 
and  multiplied  to  form  the  spot.  Explain  that  bacteria  are  studied  in 
laboratories  in  much  the  same  way. 

174.  Have  a  druggist  prepare  a  solution  of  carbolic  acid  i  to  100, 
and  of  bichloride  of  mercury  i  to  1000.  Show  the  class  how  they  should 
be  used  in  washing  the  hands  and  clothes.  Also  show  the  pure  drugs, 
and  warn  the  class  against  using  them  in  this  form.  Show  also  chloride 
of  lime  and  other  common  antiseptics. 


REVIEW  TOPICS 

Describe  yeast  and  give  its  uses  in  nature. 
Describe  mold  and  give  its  uses. 
Describe  bacteria  and  their  relation  to  decay. 
Give  the  uses  of  decay. 

Show  how  bacteria  can  enter  the  body  and  how  they 
produce  sickness. 


392 
6 

7 

8 
9 

10 

II 

12 

14 


APPLIED   PHYSIOLOGY 

Show  how  bacteria  are  destroyed  in  the  body  by  white 
blood  cells  and  by  the  blood  plasma. 

Describe  an  antitoxin  and  tell  how  it  is  used  in  treat- 
ing diphtheria. 

Describe  vaccination. 

Show  how  bacteria  are  destroyed  by  sunlight ;  by  the 
air ;  by  running  water ;  and  by  the  soil. 

Show  how  man  destroys  bacteria  by  cleanliness ;  by 
heat ;  and  by  antiseptics. 

Show  how  a  surgeon  destroys  germs  before  and  after 
a  surgical  operation. 

Give  some  hints  about  the  care  of  a  sick  room ;  and 
about  cleansing  it  after  an  infectious  disease. 

Describe  the  disease  tuberculosis,  or  consumption. 

Give  the  duties  of  a  board  of  health. 


Note.  -  —  For  a  more  extended  discussion  of  bacteria  and  disease,  see  "The 
Story  of  the  Bacteria,"  by  T.  Mitchell  Prudden,  M.D. 


CHAPTER   XLI 

REPAIR  OF   INJURIES 

694.  Injuries.  —  Many  causes  outside  the  body  operate 
upon  its  cells  to  injure  them.  Excessive  heat  or  cold  may 
impair  their  vitality  or  cause  their  death.  A  sudden  change 
from  heat  to  cold  is  a  common  cause  of  injury.  Blows  and 
cuts  may  kill  whole  armies  of  cells.  Above  all,  bacteria 
may  cause  injury  and  disease.  In  a  few  hours,  the  injured 
part  shows  a  change,  which  is  apparently  due  to  an  in- 
crease of  the  injury,  but  which  is  really  caused  by  nature's 
attempt  to  repair  the  part. 

695.  Congestion.  —  After  an  injury  has  been  received 
the  first  step  in  its  repair  is  to  dilate  the  arteries  so  as 
to  •  permit  more  blood  to  flow  through  the  part.  Then 
more  plasma  will  penetrate  into  the  lymph  spaces.  This 
produces  redness  and  some  swelling  and  is  called  conges- 
tion. Congestion  is  a  sign  of  attempted  repair.  This 
alone  may  be  sufficient  to  heal  the  injured  part. 

696.  Inflammation.  —  If  the  injury  is  greater,  there  is 
a  change  in  the  behavior  of  the  white  blood  cells.  Ordi- 
narily they  tend  to  flow  more  in  the  outer  part  of  the 
blood  stream,  but  when  the  arteries  enlarge  as  a  result  of 
injury  they  adhere  to  the  sides  of  the  smallest  blood  tubes 
and  some  pass  entirely  through  their  walls  and  lodge  in  the 
lymph  spaces.  There  they  envelop  and  digest  the  injured 
parts  and  carry  them  away  with  the  lymph.  The  lymph 
and  blood  cells  have  great  power  of  absorbing  blood  and 

393 


394 


APPLIED   PHYSIOLOGY 


dead  cells,  or  even  such  substances  as  stitches  left  in  the 
body  by  a  surgeon.  The  excess  of  white  blood  cells  causes 
more  swelling,  and  some  pain.  This  is  an  aggravated  form  of 
congestion,  and  is  called  infla^rwiation.     Some  of  the  white 

blood  cells  grow  in  place 

a 


of  the  removed  cells  and 
so  fill  in  the  gap.  Each 
cell  becomes  long  and 
branched  and  finally  de- 
velops into  a  connective 
tissue  cell.  If  the  new 
cells  are  in  great  amount, 
they  have  a  different  ap- 
pearance from  the  origi- 
nal cells  and  are  then 
called  a  scar. 

697.    Repair  of  cuts.  — 
When  a  cut  is  made  in 


©^^^^^^f#J 


Beginning  of  inflammation  ( X  400) . 

a  white  blood  cells  adhering  to  the  wall  of  a 
capillary  and  passing  through  it. 

b  white  blood  cells  which  have  passed  outside 
of  the  capillary  in  order  to  repair  an 
injury. 

c  red  blood  cells  passing  through  the  capil- 
lar}'. 

d  wall  of  capillary. 


a  tissue,  the  same  proc- 
ess takes  place,  but  in  addition  new  blood  tubes  sprout 
from  each  side  of  the  wound  and  interlace  in  the  middle. 
The  white  blood  cells  grow  about  the  new  tubes  and 
become  connective  tissue  and  so  bind  the  edges  of  the 
cut  together. 

When  the  skin  is  injured,  the  white  blood  cells  form 
new  tissue  upon  the  surface  while  the  epithelium  spreads 
over  it  from  the  edges,  stopping  the  growth  and  complet- 
ing the  healing  process.  Sometimes  the  new  connective 
tissue  grows  faster  than  the  epithelium  and  forms  soft 
tufts,  which  project  above  the  healthy  flesh.  These  tufts 
are  called  proud  flesh.  If  they  are  scraped  off,  or  cauter- 
ized, the  epithelium  is  enabled  to  cover  the  wound,  and 
to  complete  the  healing. 


REPAIR  OF  INJURIES 


395 


698.  Injuries  due  to  bacteria.  —  If  bacteria  cause  the 
injury  to  the  cells  or  if  they  enter  and  grow  after  the 
injury  is  done,  the  blood  cells  must  fight  them  as  well  as 
repair  the  damage.  Sometimes  they  cannot  do  both  at 
once.  Then  the  white  blood  cells  and  plasma  leave  the 
blood  tubes  to  a  still  greater  degree  and  lay  siege  to  the 
bacteria  until  they 
completely  fill  the 
lymph  spaces.  They 
even  stop  up  the 
blood  tubes,  produc- 
ing great  swelling 
and  pain.  White 
blood  cells  and  bac- 
teria are  now  tightly 
wedged  among  the 
injured  tissues  with 
no  chance  for  escape 
and  with  no  nourish- 
ment. Then  the 
whole  injured  part 
becomes  soft 
finallv     bursts 


The  repair  of  a  wound  (x  200 j. 


and 
and 


a   new  white  blood  cells  upon  the  surface  of  a  raw 

spot. 
b   growing  white  blood  cells. 
c    new  capillary. 
d  new  branch  from  a  capillary. 
e    older   white    blood    cells  which    are   becoming 

elongated  and  branched  like  connective  tissue 

cells. 

runs  out  as  a  creamy     /  old  capillary  sending  out  a  new  branch. 
Ill,  p-  old  connective  tissue. 

matter    called    pus.    ^ 

Thus  nature  sacrifices  a  part  of  the  body  in  order  to  get 
rid  of  the  bacteria  which  threaten  to  overcome  the  whole 
body.  Then  the  white  blood  cells  grow  and  repair  the 
wound  as  in  clean  wounds.  A  mass  of  pus  in  the  body  is 
called  an  abscess.  Every  abscess  or  collection  of  pus  is 
caused  by  bacteria. 

If  bacteria  grow  upon  an  open  cut.  the  white  blood  cells  must  devote 
part  of  their  energies  to  fighting  them,  and  so  healing  goes  on  slowly, 


39^ 


APPLIED  PHYSIOLOGY 


while  the  dead  cells,  or  pus  and  plasma,  run  off  in  a  continuous  stream. 
So  bacteria  hinder  the  repair  of  wounds,  and  prevent  their  edges  from 
growing  together  directly.  Then  the  cut  must  slowly  heal  from  its 
"*pottom.  When  a  w^ound  begins  to  be  tender  and  to  discharge,  it  is 
said  that  one  has  taken  cold  in  it.  Taking  cold  in  a  wound  means 
that  bacteria  are  growdng  in  it.  Their  toxins  may  poison  the  whole 
body  and  produce  a  severe  fever,  which  may  cause  death.  Surgeons 
now  exclude  bacteria  from  the  wounds  which  they  make.  The  white 
blood  cells  then  have  nothing  to  do  but  repair  the  cut,  and  every  part 
of  the  wound  heals  at  once.  Healing  applications  do  good  mainly  by 
destroying  germs  which  may  come  near  the  wound. 

699. 

flamed 


Treatment  of  in- 
wounds.  —  A 
tender  discharging 
wound  should  be 
cleaned  with  boiled 
water,  and  covered  with 
a  clean  antiseptic  dress- 
ing, to  soak  up  the  dis- 
charges and  bacteria. 
The  dressings  should 
be  changed  as  soon  as 
they  become  full  of 
matter.      In    this   way 

the  germs  will  be  removed,  and  the  white  blood  cells  will 

grow  unhindered. 

When  an  abscess  is  forming,  the  heat  of  a  poultice  dilates  the  blood 
vessels,  and  so  hastens  the  softening  process.  Thus  it  "brings  the 
abscess  to  a  head"  and  hastens  the  discharge  of  the  pus.  Since  the  pus 
will  form  anyhow,  it  is  always  better  to  open  the  abscess  and  let  out 
the  matter  at  once.     This  can  be  done  without  pain  by  using  cocaine. 

700.  Taking  cold  upon  the  lungs. — When  a  mucous 
membrane  is  injured,  as  by  exposure  to  cold,  there  will 
be  the  same  changes  in  its  blood  tubes  as  in  a  wound 


The  second  stage  of  inflammation  (x  200). 

a  white  blood  cells  which  have  left  the  capillary. 
b   white  blood   cells   which    nearly   block   the 

capillary. 
c   a  few  red  blood  cells  which  still  circulate. 
d  wall  of  the  capillary. 


REPAIR  OF  INJURIES 


397 


of  the  flesh.  Then  the  membrane  will  be  red  and  tender 
and  possibly  swollen.  Owing  to  the  thinness  of  the  mem- 
brane and  of  its  epithelium,  the  plasma  and  white  blood 
cells  will  come  to  the  surface.  The  matter  may  collect 
until  it  is  coughed  up  and  expelled.  The  nose  and  throat 
are  the  most  often  affected,  but  in  severe  cases  it  extends 
to  the  trachea  and  lungs.  When  the  matter  fills  the  air 
sacs  of  a  part  of  the  lung,  the  disease  is  called  piieiimonia. 

b 


The  third  stage  of  inflammation,  or  the  formation  of  an  abscess  ( x  50) . 

a  epithelium  of  the  skin  softened  and  bursting. 

b   white  blood  cells  which  have  packed  the  tissues  full  and  shut  out  nourishment. 

c   blood  tube  stopped  by  white  blood  cells. 


In  order  to  take  cold  there  must  be  an  injury  to  the  cells,  and 
bacteria  must  grow  upon  the  injured  spot.  It  often  happens  that  the 
cells  are  exposed  to  injury,  and  no  cold  is  contracted,  for  germs  do 
not  happen  to  grow,  while  on  the  other  hand  the  exposure  may  be 
slight,  and  yet  may  enable  germs  to  produce  a  severe  cold. 

In  colds  and  in  an  abscess,  the  pus  and  discharged  substances  are 
not  foul  matters  which  are  circulating  in  the  blood,  and  which  should 
be  expelled,  but  consist  of  the  strong  blood  cells  which  have  died 
fighting  for  the  defense  of  the  body,  and  of  plasma,  which  is  an  efficient 
protection  against  the  germs.  Both  being  dead  and  charged  with  the 
toxins  of  the  bacteria,  they  should  be  expelled  from  the  body. 


398  APPLIED   PHYSIOLOGY 

When  a  cold  is  first  coming  on,  a  hot  bath  and  hot  drinks  and  hot 
bed  clothing,  together  with  a  liver  stimulant,  may  cause  the  skin  and 
liver  to  excrete  enough  toxins  to  enable  the  white  blood  cells  to  over- 
come the  bacteria. 

701.  A  long  life.  —  Although  in  former  times  man  was 
often  conquered  by  bacteria  of  disease  and  even  now  is 
continually  assailed,  yet  now  he  knows  more  about  his  tiny 
foes  and  is  able  to  protect  himself.  He  knows  that  his 
eating,  his  breathing,  his  work,  his  rest,  and  in  fact  his 
every  action  will  render  his  cells  either  more  or  less  able 
to  combat  with  disease  germs.  If  all  men  would  live  up 
to  their  knowledge,  germs  of  disease  would  find  no  lodg- 
ment in  the  body,  while  there  would  be  no  cause  of  dis- 
ease in  the  body  itself.  Then  man's  mind  would  remain 
with  his  body  far  beyond  the  allotted  three  score  and  ten 
years,  and,  during  all  its  long  stay,  would  find  the  body  a 
willing  servant  to  build  the  ideal  plans  of  the  spirit  into 
enduring  realities. 

SUMMARY 

1.  An  injury  to  the  cells  of  the  body  causes  the  arteries  to 

dilate  and  bring  more  blood  to  the  part. 

2.  Over  a  sore  spot  the  white  blood  cells  form  new  con- 

nective tissue  while  the  epithelium  of  the  healthy 
skin  spreads  over  the  new  tissue,  stopping  its  growth 
and  completing  the  healing  process. 

3.  When  bacteria  are  growing  in  an  injured  spot,  the  white 

blood  cells  attack  them,  but  are  often  killed  them- 
selves and  pass  off  as  creamy  matter  called  p2is. 

4.  If  the  white  blood  cells  cannot  overcome  the  bacteria, 

they  hem  them  in  until  they  and  the  tissues  starve 
and  run  out  as  pus. 


REPAIR  OF   INJURIES  399 

5.  The  changes  which   take  place  about  an  injured  part 

cause  it  to  become  red,  painful,  swollen,  and  warmer 
than  usual. 

6.  If  wounds  and  all  other  injuries  were  protected  against 

bacteria,  they  would  heal  at  once  without  discharg- 
ing pus  or  other  matter. 

7.  In  injuries  to  mucous  membranes,  the  white  blood  cells 

and  plasma  pass  through  the  thin  tissues  to  the  sur- 
face and  are  discharged  at  once. 

8.  Taking  cold  means  an  injury  due  to  bacteria. 

9.  The  matter  discharged   from    an    abscess    or   from    a 

"cold"  is  composed  of  the  best  cells  of  the  body 
which  have  died  in  its  defense. 


DEMONSTRATIONS 

175.  Scratch  the  skin  upon  the  lower  part  of  the  arm.  Notice  that  a 
red  line  develops  in  a  moment.  Explain  that  the  scratch  injured  the 
cells  and  partly  paralyzed  the  blood  vessels,  and  that  the  redness  is  due 
to  more  blood  in  the  part,  which  has  come  to  repair  the  damage  and  to 
protect  the  rest  of  the  body. 

176.  A  pimple  upon  the  face  will  illustrate  the  different  stages  of 
inflammation.  Explain  that  a  pimple  maybe  caused  by  a  prick  too  small 
to  be  noticed,  but  which  has  introduced  some  bacteria  beneath  the  skin. 
Explain  that  the  redness  is  due  to  the  blood  which  has  come  to  repair 
the  damage.  Explain  that  the  white  spot  upon  the  top  of  the  pimple  is 
the  softened  area  through  which  bacteria  and  dead  cells  will  finally  pass 
out,  and  that  the  pus  is  composed  of  white  blood  cells  which  have  died 
fighting  to  protect  the  body  against  the  bacteria. 

177.  Place  a  tiny  drop  of  matter  pressed  from  a  pimple  or  a  cut  or  a 
scratch  upon  a  microscope  slide  and  examine  it  with  a  power  of  400 
diameters.  Notice  that  it  is  composed  of  white  blood  cells,  containing 
nuclei.  Examine  also  a  drop  of  mucus  from  the  nose  and  notice  that  it 
consists  largely  of  the  same  kind  of  cells. 

178.  Obtain  a  prepared  microscopic  specimen  from  a  wound  in  the 
process  of  healing.     Show  that  the   newly  formed  tissue  consists   of 


400  APPLIED   PHYSIOLOGY 

round  blood  cells  upon  its  surface,  and  that  in  the  deeper  layers  the 
cells  grow  larger  and  become  branched.  Explain  that  the  deeper  layers 
are  the  older  and  that  their  cells  are  white  blood  cells  which  are  grow- 
ins:  to  become  connective  tissue. 


REVIEW    TOPICS 

1.  Explain  in  order  what  happens  in  an  injured  part  of 

the  body,  describing  the  increased  flow  of   blood, 
and  the  action  of  the  white  blood  cells. 

2.  Explain  the  healing  of  a  cut. 

3.  Explain  how  a  raw  spot  of  skin  becomes  healed,  and 

what  part  the  epithelium  takes  in  the  process. 

4.  Explain  how  bacteria  in  an  injured  part  retard  healing. 

5.  Explain  how  white  blood  cells  overcome  the  bacteria. 

6.  Explain  the  formation  of  an  abscess. 

7.  Explain  taking  cold  in  a  wound,  and   in   a   mucous 

membrane. 

8.  Give  the  signs  of  inflammation  and  its  use. 

9.  Tell  what  composes  the  matter  discharged  from  an 

abscess  and  from  the  nose  and  throat  during  a  cold. 

10.  Show  how  to  treat  a  wound  in  which  one  has  taken 

cold. 

1 1 .  Explain  how  to  treat  a  cold  of  the  air  passages. 


GLOSSARY. 

Ab-do'men  (Lat.  abdometi,  belly),  the  cavity  of  the  body  which  contains 
the  stomach,  intestine,  liver,  pancreas,  and  spleen. 

Ab'scess  (Lat.  abs,  away,  and  cedere,  to  move),  a  collection  of  dead 
creamy  matter  in  the  flesh  of  a  living  person. 

Ab-sorp'tion  (Lat.  ab,  away,  and  sorbere^  to  soak  in),  taking  a  substance 
into  the  tissues  of  the  body,  without  change  in  its  composition. 

Ac-com-mo-da'tion  (Lat.  ad^  to,  con,  with,  and  modus,  measure),  adjust- 
ing the  lens  of  the  eye  to  the  proper  shape  to  cause  the  image  of  an 
object  to  fall  upon  the  retina. 

A'cid  (Lat.  acere,  to  sour),  any  sour,  irritating  substance,  which  will 
corrode  other  substances. 

A'con-ite  (Gr.  akoniton,  the  plant  commonly  called  monkshood),  an 
extremely  poisonous  plant.  It  is  used  to  lower  fevers.  In  over- 
doses it  produces  extreme  weakness  of  the  whole  body. 

Ad'e-noid  vegetations  (Gr.  adeji,  gland,  and  eidos,  form),  collections  of 
soft,  grape-like  bodies  growing  in  the  upper  part  of  the  pharynx. 
They  are  common  in  children. 

A-dul'ter-ate  (Lat.  ad,  to,  and  alter,  another),  to  make  impure  by  an 
admixture  of  an  inferior  substance. 

Al-bu'min  (Lat.  albus,  white,  because  it  generally  turns  white  when 
heated),  a  term  applied  to  a  class  of  substances,  some  form  of  which 
is  the  essential  part  of  every  living  cell.  It  is  composed  of  the 
elements  carbon,  hydrogen,  nitrogen,  oxygen,  and  sulphur.  The 
form  of  albumin  which  is  found  in  the  white  of  an  ^^;g  is  spelled 
albionen. 

Al'co-hol  (Ar.  al-kohl,  a  powder  of  antimony  used  in  painting  the 
eyebrows),  on  account  of  its  extreme  fineness  the  name  came  to  be 
applied  to  the  product  formed  by  repeatedly  distilling  wine,  for  thi.s 
was  supposed  to  be  the  real  "  spirits  "  of  the  wine. 

ov.  PHYSIOL.  —  26  401 


402  GLOSSARY 

Al-i-men'ta-ry  (Lat.  alere^  to  feed),  having  nourishing  qualities  capable 
of  being  used  as  a  food,  or  pertaining  to  food. 

Al'ka-li  (Ar.  «/,  the,  and  kali,  a  plant  whose  ashes  were  used  in  making 
glass),  a  substance  whose  properties  are  in  contrast  with  those  of 
an  acid.     An  alkali  forms  soap  when  united  with  an  oil. 

Al'ka-loid  (Ar.  alkali,  and  eidos,  form),  the  substance  in  certain  vege- 
table drugs  which  gives  the  drugs  their  characteristic  qualities.  A 
small  dose  of  an  alkaloid  produces  the  same  effect  as  a  large  dose 
of  the  drug  from  which  it  is  derived. 

A-me'ba  (Gr.  amoibe,  change),  the  simplest  form  of  animal  life,  con- 
sisting of  a  single  lump  of  jelly,  capable  of  changing  its  shape  at  will, 

Am-y-lop'sin  (Gr.  amnion,  starch),  the  ferment  in  the  pancreatic 
juice  which  changes  starch  to  glucose. 

A-nat'o-my  (Gr.  ana,  up,  and  temnein,  to  cut),  the  science  which  tells 
of  the  structure  of  living  bodies. 

An-e'mia  (Gr.  a,  without,  and  hai7na,  blood),  the  state  of  the  blood  in 
which  there  are  too  few  red  blood  cells  and  too  little  plasma. 

An-es-the'si-a  (Gr.  an,  not,  and  aisthatiesthai,  to  perceive),  a  tempo- 
rary lack  of  sensibility  produced  by  drugs. 

An'ti-dote  (Gr.  anti,  against,  and  didonai,  to  give),  a  substance  which 
prevents  a  poison  from  acting  upon  the  cells  when  it  is  introduced 
into  the  body. 

An-ti-sep'tic  (Gr.  anti,  against,  and  sepein,  to  rot),  a  substance  which 
prevents  the  growth  of  bacteria,  and  hence  prevents  rotting. 

An-ti-tox'in  (Gr.  anti,  against,  and  toxikon,  poison),  a  substance  which 
is  produced  in  the  body  to  overcome  the  poison  of  a  disease.  It  is 
commonly  applied  to  a  substance  used  in  the  treatment  of  diphtheria. 

An'trum  (Gr.  atttron,  a  cave),  the  hollow  cavity  within  the  upper  jaw 
bone. 

A-or'ta  (Gr.  aeirein,  to  lift  up),  the  large  artery  which  rises  from  the 
left  side  of  the  heart,  and  distributes  blood  to  all  parts  of  the  body. 

Ap-o-plex'y  (Gr.  apo,  from,  and  plessein,  to  strike),  a  sudden  loss  of 
consciousness,  usually  due  to  pressure  upon  the  brain  caused  by  a 
burst  artery. 

Ap-pen-di-ci'tis,  inflammation  of  the  vermiform  appendix. 

Ap'pe-tite  CLat.  ad,  to,  and  peter e,  to  seek  or  long  for),  a  strong  desire 
for  something.     It  is  used  mainly  of  the  desire  for  eating  and  drinking. 

A'que-ous  hu'mor  (Lat.  aqua,  water,  and  humor,  a  liquid),  the  liquid 
which  fills  the  eyeball  in  front  of  the  lens. 


GLOSSARY  403 

Ar'gon  (Gr.  ^,  not,  and  ergon,  work),  a  gas  (discovered  in  1894)  which 
forms  about  one  per  cent  of  the  air.     It  resembles  nitrogen. 

Ar'sen-ic  (Gr.  arsenikon),  a  gray  metal  whose  combinations  with  oxy- 
gen are  very  poisonous. 

Ar'ter-y  (Gr.  aer,  air,  and  terein,  to  hold),  the  tubes  which  conduct 
blood  to  the  cells  of  the  body.  After  death  they  are  empty,  and  it 
was  formerly  supposed  that  in  life  they  contained  only  air. 

As-phyx'i-a  (Gr.  <2,  not,  and  sphuzein,  to  throb),  death  by  suffocation. 

As-sim-i-la'tion  (Lat.  ad,  to,  and  shnilis,  like),  the  process  of  chang- 
ing digested  food  to  substances  like  those  which  compose  the  body. 

A-stig'ma-tism  (Gr.  a,  not,  and  stigma,  a  point),  the  condition  of  an 
eye  in  which  one  part  of  the  rays  are  brought  to  a  focus  sooner  than 
another  part. 

Au'ri-cle  (Lat.  auris,  an  ear),  the  upper  two  cavities  of  the  heart. 
They  are  thin  and  resemble  dog's  ears. 

Bac-te'ri-um  (pi.  bacteria)  (Gr.  bacterioti  a  staiT),  the  simplest  and 

smallest  form  of  plant  life,  consisting  of  a  tiny  sphere  or  rod.    Some 

kinds  can  grow  in  the  human  body  and  produce  disease. 
Bel-la-don'na  (Ital.  bella,  beautiful,  and  dotma,  lady),  an  herb  which 

produces  excitement  of  the  brain  and  great  weakness.     It  enlarges 

the  pupils  of  the  eyes,  and  was  formerly  used  by  ladies  to  render 

themselves  more  beautiful. 
Bi'ceps  (Lat.  bis,  twice,  and  caput,  head),  the  muscle  upon  the  front  of 

the  upper  arm  which  bends  the  elbow.      Its  upper  end  has  two 

branches. 
Bi-chlo'ride  of  mer'cu-ry,  a  compound  of  mercury  and  chlorine.     It 

is  very  poisonous  especially  to  bacteria  of  disease.    When  dissolved 

in  water  in  the  proportions  of  one  part  to  five  thousand,  it  kills 

disease  germs. 
Bi-cus'pid   (Lat.  bis,  twice,  and  aispis,  a  point),  the  fourth  and  fifth 

teeth  from  the  middle  upon  each  side  of  each  jaw ;  each  bicuspid 

ends  in  two  points. 
Bile  (Lat.  bilis),  a  yellow,  bitter  fluid  formed  by  the  liver  cells  and 

poured  into  the  intestine.     It  is  a  part  of  the  waste  of  the  body, 

but  while  it  is  being  excreted  it  assists  the  pancreatic  juice  and 

intestine  in  performing  their  work. 
Bil-i-m'bin  (Lat.  bilis,  bile,  and  ruber,  red),  the  coloring  matter  of 

the  bile.     It  consists  of  broken  down  hemoglobin. 


404  GLOSSARY 

Blad'der,  a  thin  muscular  bag  in  which  a  fluid  is  stored  in  the  body. 
It  is  especially  applied  to  the  bag  in  the  pelvis  containing  urine. 

Brain,  the  mass  of  nerve  cells  and  nerve  fibers  which  is  inclosed  with- 
in the  skull.     It  is  the  seat  of  the  consciously  acting  mind. 

Bright's  disease,  almost  any  disease  of  the  kidneys.  Dr.  Bright 
gave  the  first  true  description  of  kidney  diseases.  He  died  in 
1858. 

Bron'chus  (Gr.  brogchos,  the  windpipe),  one  of  the  numerous  branches 
into  which  the  trachea  divides.  It  is  applied  to  the  smallest  sub- 
divisions as  well  as  to  the  two  main  branches. 

Bun'ion,  a  swelling  of  the  great  toe  joint  caused  by  tight  shoes. 

But'ter-ine,  artificial  butter  made  from  butter  and  suet. 

Cae'cum  (Lat.  caecus,  blind),  the  blind  or  closed  end  of  the  large 
intestine ;  the  small  intestine  opens  into  the  side  of  large  intestine 
about  an  inch  from  its  end. 

Caf-fe-ine  {ka-fe'hi)^  a  white,  bitter  alkaloid  obtained  from  coffee. 

Callus  (Lat.  callus)^  hard  and  thickened  epidermis.  It  is  caused  by 
rubbing  a  part  during  hard  work,  and  is  naturals  way  of  protecting 
the  deeper  parts  from  injury. 

Can-cellous  (Lat.  cancelli,  a  lattice),  having  an  open  or  porous  struc- 
ture. 

Cap'il-la-ry  (Lat.  capillus^  a  hair),  a  hair-like  blood  tube.  Capillaries 
surround  each  cell  of  the  body.  From  them  plasma  and  oxygen 
go  out  from  the  blood  to  nourish  the  cells. 

Car-bol'ic  acid  (Lat.  carbo^  coal,  and  oleum,  oil),  a  poisonous  sub- 
stance obtained  from  coal  tar.  It  is  commonly  used  to  kill  dis- 
ease germs  and  to  prevent  decay. 

Car'bon  (Lat.  carbo,  coal),  a  substance,  of  which  the  diamond  is  the 
pure  crystallized  form.  Coal,  charcoal,  and  lampblack  are  more 
common  forms.  Combined  with  other  substances  it  is  a  part  of 
the  bodies  of  all  animals  and  plants. 

Car-bon'ic  acid  gas,  a  heavy,  colorless  gas  formed  when  carbon  burns. 

Car'di-ac  (Gr.  kardia,  heart),  pertaining  to  the  heart.  It  is  also 
applied  to  the  left  end  of  the  stomach,  which  lies  just  under  the 
heart. 

Car'pal  bones  (Gr.  karpos,  wrist),  the  bones  of  the  wrist. 

Car'ti-lage  (Lat.  cartilagd),  the  soft  substance  commonly  called  gristle 
which  covers  the  ends  of  bones  within  joints. 


GLOSSARY  405 

Casein  {ka'se-in)  (Lat.  casetis,  cheese),  the  part  of  the  albumin  of 
milk  which  forms  the  curd  or  clabber.  In  cow's  milk  nearly  all 
the  albumin  is  casein.  The  remaining  albumin  coagulates  and 
forms  a  scum  when  the  milk  is  heated. 

Cat'a-ract  (Gr.  kata,  down,  and  rhegtmnai,  to  break),  a  cloudiness  of 
the  lens  of  the  eye  which  shuts  out  the  light. 

Catarrh  {katar')  (Gr.  kata,  down,  and  rhein,  to  flow),  an  excessive 
production  of  mucus  from  the  nose  and  throat. 

Cells  (Lat.  cella,  a  cavity),  the  smallest  particles  of  the  body  capable  of 
fulfilling  the  tests  of  life. 

Cel'lu-lose  (Lat.  celhda,  a  little  cell),  a  substance  which  forms  most  of 
the  framework  of  vegetable  tissues. 

Ce-ment'  (Lat.  caemenhwt,  a  builder's  stone),  the  soft  bone-like  sub- 
stance which  fixes  the  teeth  in  their  sockets  in  the  jaws. 

Cer-e-bellum  (Lat.  cerebelluvi,  little  brain),  the  rounded  part  of  the 
brain  situated  under  the  cerebrum  and  above  the  medulla.  It 
assists  the  brain  to  direct  precise  movements,  as  movements  in 
which  the'  body  is  balanced. 

Cer'e-bmm  (Lat.  cerebnmi,  brain),  the  uppermost  part  of  the  brain. 
In  man  it  covers  all  the  rest.  It  is  the  seat  of  consciousness  and 
of  thought.  It  receives  all  sensations,  and  sends  all  voluntary  im- 
pulses to  produce  motion. 

Chem'is-try,  the  science  of  the  composition  of  substances.  It  is 
concerned  in  destroying  or  decomposing  substances,  and  in  form- 
ing new  substances  having  different  properties  from  the  original 
substances. 

Chlo'ral  {klo'ral),  a  substance  made  from  chlorine  and  alcohol  and  used 
to  produce  sleep. 

Chlo'ride  {kid ride) ,  a  combination  of  the  gas  chlorine  with  another 
substance.  Chloride  of  lime  is  used  to  kill  disease  germs.  Chlo- 
ride of  sodium  is  common  salt. 

Chlo'ro-form,  a  volatile  liquid  made  from  chlorine  and /i7r?;y'/.  When 
its  vapor  is  inhaled  for  some  minutes  it  produces  a  deep  sleep  and 
complete  insensibility  to  pain.  When  its  inhalation  is  stopped, 
consciousness  soon  returns.     It  is  used  in  surgical  operations. 

Chlo'ro-phyll  (Gr.  chloros,  green,  and  phullon,  leaf),  the  green  coloring 
matter  of  leaves.     It  forms  starch  out  of  carbonic  acid  and  water. 

Chol'e-ra  (Gr.  chole,  bile),  a  contagious  disease  of  the  intestine  in  which 
there  is  great  pain,  and  an  increased  excretion  and  peristalsis. 


406  GLOSSARY 

Cho'roid  (Gr.  chorion^  skin,  and  eidos,  form),  the  middle  lining  of  the 
eye.  It  carries  the  blood  vessels  for  the  nourishment  of  the  inner 
parts  of  the  eye . 

Chyle  {kile)  (Gr.  chulos,  juice),  the  liquid  produced  by  intestinal  di- 
gestion. 

Ch^rme  {kime)  (Gr.  chumos,  juice),  the  partly  digested  contents  of 
the  stomach  as  they  enter  the  intestine.  The  word  is  falling  into 
disuse. 

Cilia  {sil'i-a)  (Lat.  cilia,  eyelashes),  microscopic  hairs  upon  the  surface 
of  certain  cells.  They  are  in  constant  motion  to  sweep  out  secre- 
tions and  dust.    They  line  the  trachea  and  bronchi. 

Clab'ber,  or  bonny-clabber  (Irish  baine,  milk,  and  clabar,  mud),  sour 
and  curdled  milk. 

Clav'i-cle  (Lat.  clavis,  a  key),  the  slender  bone  which  extends  from  the 
breast  bone  to  the  shoulder.     The  collar  bone. 

Co-ag-u-la'tion  (Lat.  cofi,  together,  and  agere,  to  force),  the  process 
of  changing  a  liquid  to  a  solid  form  of  a  different  nature  from  the 
original  liquid.  Thus  in  curdled  milk  coagulation  has  taken 
place. 

Cocaine  {ko'ca-iii),  3.  bitter,  white  substance  obtained  from  coca.  It 
benumbs  pain  when  applied  to  the  nerves  and  produces  excitement 
of  the  brain. 

Coccyx  (kok'six)  (Gr.  kokkux,  a  cuckoo),  the  small  bone  which  forms 
the  lower  end  of  the  backbone.  It  is  shaped  somewhat  like  a 
cuckoo's  bill. 

Cochlea  {kok'le-d)  (Lat.  cochlea,  snail  shell),  the  coiled  canal  of  the 
inner  ear  in  which  the  nerves  of  hearing  end. 

Cold,  an  unhealthy  state  of  a  part  of  the  body  caused  by  exposure  to 
coldness  and  dampness.  It  is  an  increased  activity  of  the  cells  and 
an  increased  blood  supply  due  to  nature's  attempt  to  repair  the 
injury  caused  by  the  exposure.  The  injury  is  usually  due  *-o  the 
growth  of  disease  germs. 

Colon  (Gr.  kolo7i),  the  large  intestine. 

Con-ges'tion  (Lat.  con,  together,  and  gerere,  to  bring),  overfullness  of 
the  blood  tubes  of  a  part  of  the  body.  It  is  the  first  stage  of  repair 
of  wounds  and  of  inflammation,  and  is  nature's  way  of  supplying  an 
excess  of  nutrition  to  repair  an  injured  spot. 

Con-junc-ti'va  (Lat.  conjimctivus,  joined  together),  the  mucous  mem- 
brane lining  the  eyelids  and  covering  the  front  of  the  eyeball. 


GLOSSARY  407 

Connective  tissue,  the   stringlike  cells  scattered   through   the  whole 

body  to  keep  the  other  cells  of  the  body  in  place. 
Conservation  of  energy,  the  law  that  no  force  is  destroyed,  but  can  be 

recovered  as  heat,  electricity,  motion,  or  in  other  forms. 
Contagious  disease  {kon-ta'jus)    (Lat.   contagio,  a  touch),  a   disease 

which  can  be  transmitted  through  the  air. 
Con-trac'tion  (Lat.  cofi,  together,  and  trahere,  to  draw),  the  shortening 

and  thickening  of  a  muscle  to  produce  movement  in  a  part  of  the 

body. 
Cook  (Lat.  cogjiere),  to  prepare  food  by  the  use  of  heat. 
Cor'ne-a  (Lat.  corneus,  horny),  the  round,  bulging  window  in  the  front 

of  the  eyeball  through  which  light  enters  the  eye. 
Cor'pus-cle  (Lat.  corpusculnin^  a  little  body),  one  of  the  cells  which  float 

in  the  plasma  of  the  blood. 
Cra'ni-al  (Gr.  kr anion,  skull),  pertaining  to  the  contents  of  the  skull 

or  brain. 
Cricoid  cartilage  {kri'koid)  (Gr.  krikos,  a  ring,  and  eidos,  form),  the 

ring  which  forms  the  lower  part  of  the  larynx. 
Cud,  the  food  which  most  cloven-hoofed  animals  bring  up  from  the 

stomach  to  chew  the  second  time. 
Cu'ti-cle  (Lat.  ciitiada,  little  skin),  the  outer  and  insensitive  layer  of 

skin.     The  epidermis. 
Cu'tis  (Lat.  cutis,  skin).     A  more  common  name  is  the  derma. 

Deg'lu-ti'tion  (Lat.  de,  from,  2ind.  ghitire,  to  swallow),  swallowing. 

De-lirl-um  (Lat.  delirare,  to  rave),  a  state  of  mind  in  which  judgment 
and  reason  are  disordered  and  illusions  of  the  senses  are  present. 
It  is  usually  caused  by  fevers. 

Delirium  tre'mens,  a  form  of  delirium  which  occurs  in  drunkards.  It 
causes  the  sufferer  to  struggle  violently  to  escape  the  torments  of  his 
imagination. 

Der'ma  (Gr.  derma,  skin),  the  true  skin,  or  the  part  beneath  its  insen- 
sitive covering. 

Di'a-phragm  (Gr.  dia,  through,  2indi  phragnunai,  to  fence),  the  muscu- 
lar partition  extending  across  the  cavity  of  the  body  and  dividing 
the  chest  from  the  abdomen.     It  is  the  main  muscle  of  breathing. 

Diastole  {di-as' to-le)  (Gr.  dia,  through,  and  stellein,  to  place),  the 
relaxation  of  the  heart  during  which  it  is  being  filled  with  blood  in 
preparation  for  another  beat. 


408  GLOSSARY 

Diffusion  (Lat.  difftisio)^  the  act  of  passing  through  membranes  appar- 
ently impervious .  Thus,  peptone  passes  by  diffusion  through  the  sides 
of  the  blood  tubes  in  the  walls  of  the  intestine,  and  reaches  the  blood. 

Di-ges'tion  (Lat.  dis,  apart,  and  gerere,  to  carry  or  wear),  changing  food 
into  such  forms  that  it  can  pass  through  the  walls  of  the  blood 
tubes  and  become  a  part  of  the  blood. 

Diph-the'ri-a  (Gr.  diphthera,  leather),  an  infectious  disease  in  which 
there  is  a  skin-like  membrane  covering  the  affected  part,  usually  the 
throat. 

Dis-lo-ca'tion  (Lat.  dis,  apart,  and  locare,  to  locate),  the  separation  of 
two  bones  whose  union  forms  a  joint. 

Dis-til-la'tion  (Lat.  de,  from,  and  stillare,  to  drop),  the  process  of  sepa- 
rating a  substance  which  easily  becomes  a  vapor  from  one  which 
forms  a  vapor  less  easily.  Heat  is  applied  to  the  substance,  and 
the  vapor  is  cooled  or  condensed  to  a  liquid  in  a  coil  of  tube  from 
which  it  runs  in  drops,  and  hence  the  name.  As  far  back  as  the 
year  1200  the  process  was  used  by  the  Arabs  in  their  endeavors  to 
find  an  essential  spiritual  principle  which  would  sustain  life  and 
restore  youth. 

Drop'sy,  a  uniform  swelling  of  a  part  without  pain  or  redness.  It  is 
an  accumulation  of  lymph  due  to  a  disturbance  in  the  circulation  of 
the  blood. 

Duct  (Lat.  ducere^  to  lead),  any  tube  which  conducts  a  secretion  away 
from  a  gland. 

Du-0-de'num  (Lat.  duodeni^  twelve),  the  beginning  of  the  small  intes- 
tine for  the  length  of  about  twelve  finger  breadths. 

Du'ra  ma'ter  (Lat.  dura,  harsh,  and  mater,  mother),  the  periosteum 
lining  the  skull.  It  is  very  thick  and  sends  prolongations  into  the 
main  fissures  of  the  brain  to  hold  the  brain  in  place. 

Dys-pep'si-a  (Gr.  dus,  ill,  and  peptein,  to  cook  or  digest),  imperfect 
digestion  of  the  food. 

E-mul'sion  (Lat.  e.  out,  and  miilgere,  to  milk),  a  milky-looking  liquid 

consisting  of  microscopic  drops  of  oil  floating  in  a  liquid. 
En-am'el,  the  hard  calcified  tissue  which  covers  the  exposed  parts  of 

the  teeth. 
En'er-gy  (Gr.  en,  in,  and  ergon,  work),  any  force  which  can  be  made 

to  do  work.     The  energy  of  the  body  can  be  traced  to  oxidation 

within  the  cells. 


GLOSSARY  409 

Ep'i-der'mis  (Gr.  epi,  upon,  and  dertna,  skin),  the  thin  insensitive 
layer  of  cells  upon  the  outside  of  the  skin.  It  is  sometimes  called 
the  cuticle. 

Ep-i-glot'tis  (Gr.  epz,  upon,  2ind glotta,  the  tongue),  the  leaf-like  lid  upon 
the  back  of  the  tongue  which  closes  the  larynx  when  swallowing. 

Ep'i-lep-sy  (Gr.  epilepsis,  a  seizure),  a  disease  in  which,  at  intervals 
a  person  suddenly  falls  to  the  ground  unconscious,  while  all  the 
muscles  of  the  body  contract  strongly. 

Ep-i-thelium  (Gr.  epi,  upon,  and  thele,  nipple),  the  cells  which  cover 
the  skin  and  mucous  membrane  and  line  the  tubes  of  glands.  Epi- 
thelium is  a  protection  for  the  body,  and  does  all  the  work  of  secre- 
tion and  absorption. 

Er-y-sip'e-las  (Gr.  eruthros,  red,  and  pella,  skin),  a  disease  of  the 
skin  in  which  there  is  pain,  redness,  and  swelling.  It  is  caused  by 
the  growth  of  bacteria  of  disease  in  a  wound.  It  varies  in  severity 
from  a  simple  maturated  scratch  to  a  severe  blood  poison. 

E-soph'a-gus  or  oe-soph'a-gus  (Gr.  oiso,  I  shall  carry,  and  phagein,  to 
eat),  the  tube  connecting  the  mouth  with  the  stomach. 

E'ther  (Gr.  aithein,  to  burn),  a  colorless  liquid  which  evaporates  with 
such  great  rapidity  that  its  vapor  may  catch  fire  if  near  a  lamp.  It 
is  used  to  dissolve  gums,  and  also,  like  chloroform,  to  produce  in- 
sensibility during  surgical  operations. 

E'ther  (Lat.  'aether,  the  upper  pure  air  where  the  gods  abode,  in  dis- 
tinction from  the  lower  or  true  air  in  which  man  hved),  the  sub- 
stance which  is  supposed  to  pervade  all  space,  and  whose  vibrations 
are  supposed  to  form  light,  heat,  and  electricity. 

Eustachian  tube  {yu-sta'ki-an),  the  tube  leading  from  the  middle  ear 
to  the  pharynx.  It  is  named  after  its  discoverer,  Eustachi,  an 
Italian  physician,  who  died  in  1574. 

Ex-cre'tion  (Lat.  ex,  out,  and  cretus,  sifted),  a  waste  substance  extracted 
from  the  blood  by  the  epithelium  of  a  gland. 

Ex-pi-ra'tion  (Lat.  ex,  out,  and  spirare,  to  breathe),  breathing  out  air 
from  the  lungs. 

Ex-ten'sor  muscles  (Lat.  ex,  out,  and  tendere,  to  stretch),  the  muscles 
which  straighten  limbs. 

Fat,  a  white   greasy  substance  composed   of  carbon,  hydrogen,  and 

oxygen,  but  with  much  less  oxygen  than  is  in  starch. 
Fe'mur  {L2X.  femur),  the  thigh  bone. 


4IO  GLOSSARY 

Fer'ment  (Lat.  fervimenUim,  boiling),  a  substance  a  small  amount  of 

which  produces  a  chemical  change  in  a  large  amount  of  another 

substance  without  losing  its  own  identity  or  characteristics.     During 

the  process  the  most  common  ferment  —  yeast  —  liberates  bubbles 

of  gas,  like  a  boiling. 
Fe'ver  {\j3ii.  febris^  a  fever),  increased  warmth  of  the  body  due  to  poisons 

of  disease. 
Fi'brin  {\j2i\..  fibra,  a  thread),  the  stringy  threads  of  coagulated  blood 

albumin  which  permeate  the  blood  and  imprison  its  cells  and  plasma, 

causing  it  to  become  jellyJike  or  clotted. 
Fib'u-la  {\jdX.  fibula,  clasp),  the  long  bone  upon  the  outside  of  the  shin 

bone. 
Fil-tra'tion  (Lat.  feltrum,  felt),  separating  a  solid  from  a  liquid  by 

straining  it  through  a  porous  substance. 
Fis'sure  (Lat.  fissura,  a  cleft),  one  of  the  deep  furrows  upon  the  sur- 
face of  the  brain. 
Fit,  a  sudden  state  of  unconsciousness  and  of  contraction  of  the  muscles 

lasting  only  a  minute  or  two.     Epilepsy  is  a  kind  of  fit. 
Flex' or    muscles    (Lat.    fleet  ere,    to    bend),    muscles    which    bend 

the  limbs. 
Fo'cus  (Lat.  focus,  a  fireplace),  the   point  where   rays  of  light  come 

together  when  passed  through  a  lens. 
Food,  anything  which  is  assimilated  by  the  body,  and  gives  it  weight, 

heat,  or  energy.     The  term  includes  water  and  mineral  matter  as 

well  as  vegetable  and  animal  substances. 
Front'al  (Lat.  frons,  the  forehead),  pertaining  to  the  region  of  the  skull 

or  brain  behind  the  forehead. 
Furcmm  (Lat.  word  meaning  a  prop),  the  fixed  support  around  which 

a  lever  turns. 

Gall  (gawl),  a  name  applied  to  the  bile  while  it  is  stored  in  the  bag 

under  the  liver. 
Gan'gli-on  (Gr.  gagglion,  a  knot),  a  collection  of  nerve  cells  in  the 

sympathetic  system.     Each  looks  like  a  grain  kernel. 
Gas'tric  (Gr.  gaster,  stomach),  pertaining  to  the  stomach. 
Gelatine  (Jel'a-tin)  (Lat.  gelare,  to  harden),  a  kind  of  albumin  which 

forms  the  principal  part  of  connective  tissue.     It  will  dissolve  in 

hot  water,  and  forms  a  jellylike  or  solid  mas5)  when  cold.     Glue  is 

an  impure  form. 


GLOSSARY  411 

Germs  (L2it.  germen,  a  bud),  a  name  loosely  applied  to  bacteria. 

Giz'zard,  the  muscular  organ  in  a  fowl's  abdomen  which  grinds  food  to 
pieces  and  acts  in  place  of  teeth. 

Gland  (Lat.  g/ans,  an  acorn),  a  collection  of  microscopic  tubes  which 
form  a  watery  substance  within  the  body. 

Glu'cose  (Gr.  glukiis,  sweet),  a  form  of  sugar  found  in  the  grape,  and 
produced  artificially  by  the  action  of  sulphuric  acid  on  starch ;  it  is 
also  produced  in  the  body  by  the  action  of  the  digestive  fluids  upon 
starch  and  sugar. 

Glu'ten  (Lat.  ghtien.,  glue),  the  albumin  of  grain. 

Gly-CO-chol'ic  acid  (Gr.  glukus,  sweet,  and  c/iole,  bile),  one  of  the  prin- 
cipal waste  substances  in  the  bile. 

Gly'co-gen  (Gr.  ghikiis^  sweet,  and  genei^i,  to  generate),  a  form  of 
sugar  to  which  digested  sugar  and  starch  is  turned  by  the  liver. 

Gout  (gowt)  (Lat.  giitta,  a  drop),  a  swelling  of  a  joint,  especially  of  the 
great  toe,  caused  by  a  disturbance  of  digestion  and  oxidation.  It 
was  formerly  supposed  to  be  due  to  a  fluid  or  humor  which  flowed 
down  in  drops  from  the  upper  parts  of  the  body. 

Grippe  igyip)  (Fr.  grippe,  influenza),  a  kind  of  fever  which  occurs  in 
epidemics.     It  is  caused  by  the  growth  of  a  germ  in  the  body. 

Hash'eesh,  the  gum  of  a  kind  of  hemp.  It  produces  an  excited  and 
dreamy  state  of  mind. 

Ha-ver'si-an  canals,  the  minute  tunnels  in  bone  through  which  the 
arteries  run.  They  were  discovered  by  Havers,  an  English  physi- 
cian, who  lived  in  the  seventeenth  century. 

Hem-0-glo'bin  (Gk.  haivia,  blood,  and  Lat.  globus,  a  ball),  the  coloring 
matter  of  the  red  blood  cells. 

Hem-o-phil'i-a  (Gr.  haijua,  blood,  and  philein,  to  love),  a  state  of  the 
blood  in  which  it  will  not  clot. 

Hem'or-rhage  (Gr.  hai?na,  blood,  and  rhegnufiai,  to  break),  a  flow  of 
blood  from  a  blood  tube. 

Hi-ber-na'tion  (Lat.  hibenms,  wintry),  passing  the  winter  in  a  torpid 
state,  as  frogs  and  snakes  do. 

Hu'mer-us  (Lat.  humerus^,  the  long  bone  in  the  upper  part  of  the  arm. 

Hu'mors  (Lat.  humor,  moisture),  substances  which  were  formerly  sup- 
posed to  circulate  in  the  blood  and  to  cause  disease. 

Hy-dro-chlor'ic  acid,  a  compound  oi  hydrogen  and  chlorine,  commonly 
called  muriatic  acid.     It  is  a  violent  poison. 


412  GLOSSARY 

Hy-dro-gen  Qiy' dro-jai)  (Gr.  hiidor,  water,  and  genein,  to  generate),  a 
light,  colorless  gas.    When  ignited  it  unites  with  oxygen  to  form  water. 

Hygiene  (Jiy'ji-eeti)  (Gr.  hugieinos,  healthy),  the  science  which  tells 
how  to  keep  living  bodies  in  good  working  order. 

Hy-po-der'mic  injection  (Gr.  hupo^  under,  and  derma,  skin),  the  intro- 
duction of  a  solution  under  the  skin  by  means  of  a  hollow  needle 
and  syringe.  The  solution  fills  the  lymph  spaces  and  is  absorbed 
into  the  capillaries  or  enters  the  circulation  by  way  of  the 
lymph. 

Hys-te'ri-a,  a  nervous  disease  in  which  there  is  great  lack  of  self-con- 
trol. The  sufferer  easily  gives  way  to  the  emotions,  and  especially 
to  those  of  sorrow  or  mirth. 

ire-um  (Gr.  eilein,  to  twist),  the  lower  half  of  the  small  intestine. 

In-ci'sor  teeth  (Lat.  ijicidere,  to  cut  into),  the  teeth  in  front,  with  which 
food  is  bitten  into. 

Incus  {in'kus)  (Lat.  inctis,  anvil),  the  middle  bone  of  the  chain  in  the 
ear  drum^  which  transmits  waves  of  sound  from  the  drumhead  to 
the  inner  ear. 

In-fec'tious  disease  (Lat.  in,  in,  and  facere,  to  make),  a  disease  which 
has  for  its  cause  some  matter  which  can  multiply  and  grow  when 
introduced  into  the  body  of  a  healthy  man. 

In-flam-ma'tion  (Lat.  m,  in,  2indi  fiamma,  a  flame),  redness,  swelling, 
pain,  and  increased  heat  in  a  part  as  a  result  of  injury.  It  is  nature's 
attempt  to  repair  the  part.     Often  it  goes  on  to  form  matter. 

In-san'i-ty  (Lat.  in,  not,  and  sanus,  safe),  unsoundness  of  mind  per- 
sisting for  a  considerable  time. 

In-spi-ra'tion  (Lat.  in,  in,  and  spirare,  to  breathe),  taking  a  breath 
into  the  lungs. 

In-tem'per-ance  (Lat.  in,  not,  and  temperare,  to  regulate),  gratifica- 
tion of  a  desire  which  does  not  denote  a  real  need  of  the  body. 

In-tes'tine  (Lat.  intiis,  within),  the  long  tube  in  the  abdomen  in  which 
digestion  of  food  is  completed  after  it  leaves  the  stomach. 

In-tox-i-ca'tion  (Lat.  in,  in,  and  toxicum,  poison),  great  mental  excite- 
ment or  lack  of  control,  usually  due  to  alcohol. 

I'ris  (Gr.  iris,  rainbow),  the  colored  curtain  in  the  eye  behind  the  cornea. 

Jaundice  (Jakn'dis)  (Fr.  jaune,  yellow),  yellowness  of  the  skin  due  to 
a  deficient  excretion  of  bile  by  the  liver. 


GLOSSARY  413 

Je-ju'num  (Lat.  jejunus^   empty),   the   middle   portion  of  the   small 

intestine. 
Joint  {\j^\.j linger e^  to  join),  the  union  of  two  bones. 

Kid'ney,  the  organ  which  excretes  urea. 

Lab'y-rinth  (Gr.  laburmthos),  an  intricate  arrangement  of  passages. 

The  inner  ear. 
Lach'ry-mal  glands  (Lat.  lacrima,  a  tear),  the  glands  which  produce 

the  tears.    They  are  situated  in  the  orbit  just  above  the  eyeball,  upon 

its  outer  side. 
Lac'te-al   tubes  (Lat.  lac,  milk),  the  tine  lymxphatic  tubes  which  take 

up  fat  from  the  intestine.     During  digestion  they  can  be  seen  as 

milky  hues  across  the  mesentery. 
Lac-tom'e-ter  (Lat.  lac,  milk,  and  w^^rz^w,  measure) ,  an  instrument  for 

testing  the  purity  of  milk. 
Larynx  (Jah'ri7iks)  (Gr.  lariigx),  the  box  in  the  upper  part  of  the  neck 

in  which  the  windpipe  begins.     It  contains  the  vocal  cords. 
Lau'da-num,  opium  dissolved  in  nine  times  its  weight  of  alcohol. 
Lens  (Lat.  lens,  lentil),  a  transparent  substance  having  curved  surfaces. 

It  has  the  power  of  changing  the  directions  of  rays  of  light. 
Leu-co-ma-ine  {lew-ko' mah-in)  (Gr.  leitkoma,  white),  a  class  of  sub- 
stances resembling  alkaloids  which  are  found  in  the  body  during 

life.     They  are  very  poisonous,  and  much  sickness  is  due  to  their 

presence. 
Lev'er  (Fr.  lever,  to  raise),  a  pry  ;  a  rigid  bar,  one  part  of  which  is  made 

to  turn  about  a  fixed  point  called  a  fulcrum,  while  an  opposite  part 

presses  against  a  resisting  object  which  it  moves. 
Lig'a-ment  (Lat.  ligare,  to   bind),  the  fibrous   bands  of  connective 

tissue  which  bind  bones  together  to  form  joints. 
Liv'er,  the  large  red  gland  in  the  upper  right  side  of  the  abdomen.     It 

forms  bile  and  changes  digested  food  to  blood. 
Lymph  (Lat.  lyinpha,  a  spring  of  water),  the  plasma  and  white  cor- 
puscles which  have  left  the  capillaries  to  nourish  the  cells  of  the 

body. 
Lym-phat'ics,  the  tubes  which  convey  lymph  back  to  the  veins.    Lymph 

nodes  are  spongy  bodies  like  grains  of  wheat  which  strain  out  waste 

or  poisonous  substances  from  the  lymph.     In  the  neck  and  groin 

they  can  be  felt,  and  are  usually  called  kernels. 


414  GLOSSARY 

Ma-la'ri-a  (Ital.  malo,  bad,  and  aria^  air),  a  disease  caused  by  exhala- 
tions which  arise  from  decaying  vegetable  matter. 
Mal'le-US  (Lat.  malleits^  hammer),  the  first  bone  of  the  chain  of  small 

bones  which  conveys  sound  waves  across  the  tympanum. 
Malt,  grain,  usually  barley,  soaked  in  water  until  it  has  sprouted  about 

half  an  inch,  and  then  dried.     The  sprouting  changes  a  large  part 

of  the  starch  to  sugar. 
Ma'ni-a  (Lat.  jnania,  rage),  a  form  of  insanity  in  which  the  intellect 

is  so  active  that  the  judgment  cannot  control  it. 
Mar'row,  fat  which  fills  the  hollow  bones. 
Mas-ti-ca'tion   (Lat.   fnasticare,  to   chew),  properly,  the   grinding  to 

which  food  is  subjected  by  the  teeth,  tongue,  and  lips.     Usually  the 

mixing-  with  the  saliva  is  also  included. 
Mas'toid  process  (Gr.  mastos^  the  breast),  the  rounded   projection  of 

bone  situated  behind  the  ear. 
Me-dul'la  oblongata  (Lat.  viedulla^  marrow),  the  part  of  the  brain  just 

above  the  spinal  cord.     It  controls  respiration  and  the  contraction 

of  arteries. 
Mel-an-cho'li-a  (Gr.  jnelas,  black,  and  chole,  bile),  a  form  of  insanity 

in  which  a  person's  mental  actions  are  excessively  retarded.     He 

feels  downcast  and  thinks  every  one  is  avoiding  him  on  account 

of  his  sins.     It  is  the  opposite  of  mania.     It  was  formerly  supposed 

to  be  due  to  black  bile  circulating  in  the  blood. 
Mem'brane  (Lat.  me?nbraiia,  skin),  any  skin-like  part  of  the  body. 

The  membrana  tympani  is  the  skin-like  tissue  which  separates  the 

middle  ear  from  the  outer  ear. 
Mer'cu-ry  (Lat.  Merai7'ms^  the  messenger  of  the  gods),  the  liquid 

metal  commonly  called  quicksilver. 
Mes'en-ter-y  (Gr.  mesos^  middle,  and  enter  on,  intestine),  the  thin  fold 

of  peritoneum  which  holds  the  intestine  in  place. 
Met-a-car'pal  bones  (Gr.  meta,  after,  and  karpos,  the  wrist),  the  five 

slender  bones  just  below  the  wrist  which   form  the  palm  of  the 

hand. 
Met-a-tar'sal  bones  (Gr.  meta,  after,  and  tarsos,  the  flat  of  the  foot), 

the  five  long  bones  in  front  of  the  ankle  which  form  the  front  part 

of  the  foot. 
Mi'crobes  (Gr.  7mkros,  little,  and  bios,  life),  the  smallest  living  bein^ . 

Microbes  are  plants,  some  of  which  may  grow  in  the  human  body 

and  produce  diseases.     They  are  the  same  as  bacteria  and  germs. 


GLOSSARY  415 

Mi'cro-SCOpe  (Gr.  mikros,  little,  and  skopein,  to  see),  an  instrument 
which  makes  minute  objects  appear  large. 

Milk,  the  fluid  which  all  female  mammals  secrete  for  the  nourishment 
of  their  young. 

Mi'tral  (Gr.  jnitra,  a  head  covering),  the  valve  between  the  left  auricle 
and  ventricle ;  when  closed  it  resembles  a  priest's  miter  or  hat. 

Molar  (Lat.  mola,  a  mill),  a  tooth  having  a  flat  surface  for  grinding 
food.     The  last  three  teeth  on  each  side  of  each  jaw  are  molars. 

Mold,  a  low  order  of  microscopic  plants  which  usually  grow  in  the  in- 
terior of  substances.  Common  forms  send  up  spore  stalks  which 
form  the  velvety  coating  popularly  called  mold. 

Mor-phine'  (Gr.  fnorpheus,  the  god  of  sleep),  the  principal  alkaloid  of 
opium. 

Mo'tor  nerves  (Lat.  movere,  to  move),  the  nerves  which  carry  orders 
from  the  brain  or  spinal  cord  to  cause  the  cells  of  the  body  to  act. 

Mu'cous  mem'brane,  the  soft,  skin-like  membrane  lining  cavities  which 
open  upon  the  surface  of  the  body. 

Mu'cus  (Lat.  amicus),  the  thin,  slimy  fluid  produced  by  the  epithelium 
lining  the  organs  of  digestion  and  respiration. 

Mu-ri-at'ic  acid  (Lat.  miiria.  brine),  the  common  name  of  hydro- 
chloric acid.  The  acid  is  very  sour  and  corrosive.  It  combines 
with  sodium  to  form  common  salt,  but  many  of  its  combinations 
are  poisonous. 

Mus'cle  (Lat.  imisadus^  a  little  mouse),  a  collection  of  cells  which  can 
become  thicker  and  shorter  and  so  produce  motion. 

Nar-cot'ic  (Gr.  narkotm,  to  benumb),  a  substance  which  hinders  the 

action  of  nerves  and  nerve  cells  and  produces  sleep. 
Na'sal  duct  (Lat.  7iasa,  the  nose),  the  duct  which  carries  tears  from 

the  eyes  to  the  nose. 
Nerve  (Gr.  neuron,  nerve),  a  collection  of  the  threads  which  conduct 

i«ipulses  between  the  cells  of  the  body  and  the  central   nervous 

system. 
Neuritis  {new-ri' tis)  (Gr.  micron,  nerve),  inflammation  of  a  nerve. 
Neu'tral-ize  (Lat.  neuter,  neither),  to  make  neither  acid  nor  alkaline. 
Nic'o-tine,  the  active  principle  in  tobacco,  named  from  the  Frenchman 

Nicot  who  introduced  tobacco  into  France  in  1560. 
Nu'cle-O  albumin,  a  form  of  albumin  containing  iron  and  found  in  the 

nucleus  of  cells.     From  it  hemoglobin  is  formed. 


41 6  GLOSSARY 

Nu'cle-us  (Lat.  nucleus,  kernel),  a  mass  usually  distinguishable  near  the 
center  of  each  cell.    It  seems  to  be  endowed  with  special  vital  powers. 

Oc-cip'i-tal  region  (Lat.  ob,  against,  and  caput,  the  head),  the  region 
of  the  skull  or  brain  which  is  situated  farthest  back. 

0-le-o-mar'ga-rine,  a  compound  made  from  beef  fat  and  milk.  It  has 
the  properties  and  nutritive  value  of  butter. 

01-fac'to-ry  (Lat.  olere,  to  have  a  smell,  and  facere,  to  make),  pertain- 
ing to  the  sense  of  smell. 

0-men'tum  (Lat.  omentuvi),  the  fatty  apron  in  front  of  the  intes- 
tine. 

O'pi-um  (Gr,  opion,  poppy  juice),  the  dried  juice  of  a  kind  of  poppy 
growing  in  western  Asia.  It  is  a  narcotic  and  is  used  to  produce 
sleep  and  to  benumb  pain. 

Op'tic  (Gr.  optikos),  pertaining  to  sight.  The  optic  nerves  convey 
impressions  of  sight.  The  optic  tubercles  are  collections  of  gray 
matter  in  the  brain  between  the  medulla  and  cerebrum.  They  are 
reflex  centers  for  the  eye. 

Or'bit  (Lat.  or  bis,  a  circle),  the  bony  cavity  which  contains  the 
eyeball. 

Or'gan  (Gr.  organon,  a  tool),  a  collection  of  tissues  having  a  definite 
compact  form  and  purpose. 

Or-gan'ic  (Gr.  orgation,  a  tool),  a  term  designating  a  substance  built 
up  only  by  the  agency  of  living  substances. 

Ox-i-da'tion,  the  union  of  oxygen  with  another  substance.  It  is  the 
essential  part  of  the  processes  of  burning  and  of  breathing. 

Oxygen  {ox'y-jeri)  (Gr.  oxus,  sharp  or  acid,  and  genein,  to  generate),  a 
gas  forming  one  fifth  of  the  air.  Its  union  with  the  cells  of  the 
body  forms  the  essential  part  of  the  process  of  breathing. 

O'zone  (Gr.  02071,  smelling),  a  very  active  form  of  oxygen  formed  by 
electricity  and  sometimes  found  in  the  air. 

Pal'ate  (Lat.  palatum),  the  roof  of  the  mouth. 

Pal-pi-ta'tion  (Lat.  paipitare,   to   throb),  violent   throbbing   of   the 

heart,  so  that  its  beats  make  themselves  felt  through  the  chest  wall. 
Pan'ore-as  (Gr.  pan,  all,  and  kreas,  flesh),  the  gland  situated  behind 

the  stomach  which  forms  the  pancreatic  juice.     The  sweetbread. 
Pan-cre-at'ic  juice,  the  liquid  secretion  of  the  pancreas  which  digests 

albumin,  fat,  and  sugar  in  the  intestine. 


GLOSSARY  417 

Pan'ic  (Gr.  to  panikon,  from  Pan,  the  god  of  the  woods,  and  of  sudden 
fear),  a  sudden  and  infectious  fear  which  sometimes  seizes  upon  a 
crowd. 

Pa-pilla  (Lat.  papilla,  pimple),  a  minute  projection  of  the  true  skin 
into  the  epidermis.  It  contains  the  endings  of  the  nerves  of 
touch. 

Pa-ral'y-sis  (Gr.  para,  beside,  and  liiein,  to  loosen),  lack  of  action  of 
a  part  due  usually  to  a  failure  of  the  m.otor  nerves  to  bring  the  im- 
pulses for  action. 

Par-e-gor'ic  (Gr.  paregoros,  soothing),  a  sweet-tasting  mixture  contain- 
ing opium  and  used  chiefly  in  quieting  children. 

Pa-ri'e-tal  bones  (Lat.  paries,  a  wall),  the  top  and  sides  of  the 
skull. 

Pa-ro'tid  glands  (Gr.  para,  near,  and  ons,  ear),  the  salivary  glands  in 
the  front  of  the  ear. 

Pel'vis  (Lat.  pelvis,  basin),  the  massive  ring  of  bone  which  forms  the 
hips.  Its  cavity  is  somewhat  larger  than  a  large  tea  cup  and  con- 
tains some  of  the  intestine. 

Pep'sin  (Gr.  peptein,  to  cook  or  digest),  a  lifeless  ferment  found  in  the 
stomach  of  all  animals.     It  digests  albumin. 

Pep'tone  (Gr.  peptos,  cooked),  the  form  to  which  albumin  is  changed 
by  digestion. 

Per-i-car'di-um  (Gr.  peri,  around,  and  kardia,  heart),  the  thin  bag 
v/hich  surrounds  the  heart. 

Per-i-os'te-um  (Gr.  peri,  around,  and  osteon,  bone),  the  thin,  tough 
membrane  which  covers  bone,  reproduces  its  cells,  and  transmits  its 
blood  vessels  and  nerves. 

Per-i-stal'sis  (Gr.  peri,  around,  and  stellein,  to  arrange),  the  regular, 
worm-Hke  movements  of  the  alimentary  canal,  which  force  its  con- 
tents onward. 

Per-i-to-ne'um  (Gr.  peri,  around,  and  teineijt,  to  stretch),  the  thin, 
shining  membrane  which  lines  the  interior  of  the  abdomen  and 
covers  its  organs. 

Per-spi-ra'tion  (Lat.  per,  through,  and  spirare,  to  breathe),  the  watery 
secretion  of  the  skin.     The  sweat. 

Pha-lan'ges  (Gr.  phalagx,  a  rank  of  soldiers),  the  rows  of  bone  which 
form  the  fingers  and  toes.     Its  singular  is  phalanx. 

Pharynx  {far' inks)  (Gr.  phariigx,  the  throat,  from  phareiti,  to  cleave), 
the  cavity  back  of  the  nose  and  mouth. 
ov.  PHYSIOL.  —  27 


41 8  GLOSSARY 

Phos'phor-us  (Gr.  phos^  light,  and  pherein,  to  bring),  a  waxy,  yellowish 
substance  which  combines  with  oxygen  at  ordinary  temperatures, 
giving  otF  heat  and  a  faint  light.  The  light  produced  by  rubbing 
matches  is  due  to  the  phosphorus. 

Phys-i-ol'o-gy  (Gr.  phusis,  nature,  and  logos,  discourse),  the  science 
which  tells  of  the  working  of  living  bodies. 

Pi-a  ma-ter  (Lat.  pia,  pious,  and  mater,  mother),  the  delicate  cover- 
ing of  the  brain  which  carries  its  blood  vessels,  in  distinction  from 
the  thick  protecting  dura  mater. 

Plas'ma  (Gr.  plas^na,  molded),  the  liquid  part  of  blood  in  distinction 
from  the  cells  which  float  in  it.  It  is  composed  chiefly  of  water, 
albumin,  and  minerals.  It  is  food  for  the  cells  of  the  body  and  it 
washes  away  their  waste  matters. 

Pleura  {plew'ra)  (Gr.  pleura,  rib),  the  lining  of  the  chest  and  coating 
of  the  lung. 

Plex'us  {IjSiX.  pled  ere,  to  braid),  a  network  of  sympathetic  nerve  cells 
and  fibers. 

Plumb'ing  (Lat.  phmibwn,  lead),  the  pipes  which  conduct  water  and 
sew^age  in  a  house.     Many  are  made  of  lead. 

Pneumonia  {7iew-mo' ni-a)  (Gr.  pneiifnon,  a  lung),  a  disease  in  which 
the  air  sacs  of  the  lung  become  filled  with  coagulated  matters  from 
the  blood. 

Poi'son  (Lat.  potio,  a  drink),  a  substance  which  destroys  or  interferes 
with  the  life  of  the  cells,  when  it  is  taken  into  the  body. 

Por'tal  vein  (Lat.  porta,  a  gate),  the  vein  formed  by  the  union  of  the 
veins  from  the  digestive  organs.  This  vein  divides  into  the  capilla- 
ries of  the  liver.  Finally  three  veins  conduct  the  blood  to  the  ascend- 
ing vena  cava. 

Pro'to-plasm  (Gr.  protos,  first,  2ind  plasma,  form),  the  albuminous  sub- 
stance which  forms  the  body  of  every  living  cell. 

Proximate  principles,  the  elementary  substances  existing  as  such  in 
the  body. 

Ptomaine  (to'mah-in)  (Gr.  ptoma,  a  dead  body),  a  class  of  poison- 
ous substances  resembling  alkaloids  and  leucomaines,  which  are 
found  in  dead  bodies.  Their  presence  makes  decayed  food 
dangerous. 

Ptyalin  (ti'a-lin)  (Gr.  ptiiein,  to  spit),  the  lifeless  ferment  in  the  saliva 
which  changes  starch  to  sugar. 

Pul'mo-na-ry  (Lat.  piibno,  lung),  pertaining  to  the  lungs. 


GLOSSARY  419 

Pulse  (Lat.  pulsus^  a  blow),  the  wave  which  may  be  felt  in  an  artery 

with  each  heart  beat. 
Pu'pil  (Lat.  piipilla),  the  opening  in  the  iris  through  which  light  enters 

the  eye.     It  appears  as  a  round  black  spot  in  the  center  of  the  col- 
ored part  of  the  eye. 
Pus  (Lat.  puteo^  to  rot),  the  creamy  matter  which  flows  from  an  abscess. 

It  is  formed  mostly  of  dead  white  blood  cells. 
Pu-tre-fac'tion  (Lat.  piitris,  rotten,  and  facere.  to  make),  the  process 

of  decay  accompanied  by  bad  odors. 
Py-lo'nis  (Gr.  pjde,  a  gate),  the  orifice  in  the  right  end  of  the  stomach, 

through  which  food  passes  into  the  intestine. 
Py'ri-dine  (Gr.  pur^  Are),  a  poisonous  substance  formed  by  burning 

nicotine. 

Ra'di-us  (Lat.  radius,  the  spoke  of  a  wheel),  the  bone  upon  the  thumb 

side  of  the  arm,  below  the  elbow. 
Re'flex  action  (Lat.  re,  back,  2m^  fleet  ere.  to  turn),  the  action  of  the 

central  nerve  cells  in  sending  orders  for    motion    in  response  to 

an  impulse  brought  by  sensory  nerves. 
Ren'nin,  a  lifeless  ferment   extracted  from   the  lining  of  the  fourth 

stomach   of  a   calf,  and   used    to   curdle  milk   in  cheese  making. 

The  same  ferment  is  found   in  the  human  stomach,  especially  in 

infancy. 
Res- pi-ra'tion  (Lat.  re,  again,  and  spirare.  to  breathe),  the  process  of 

breathing  and  of  the  interchange  of  oxygen  and  carbonic  acid  gas 

in  the  cells  of  the  body. 
Ret'i-na  (Lat.  rete,  a  net),  the  inner  lining  of  the  eye  in  which  the 

nerves  of  sight  end. 
Rheumatism  {ru'ma-tism)  (Gr.  rheiim,  a  flowing  or  stream),  a  swell- 
ing of  the  joints  in  which  they  are  often  quickly  affected  one  after 

another.     Usually  it  is  due  to  fluid    collecting  in  the  bag  of  the 

synovial  membrane. 
Rick'ets,  a  disease  in  which  the  bones  have  too  little  lime  and  bend  too 

easily. 

Sa'crum  (Lat.  sacer,  sacred,  for  the  bone  was  offered  in  sacrifice),  the 
part  of  the  backbone  which  completes  the  pelvis  behind. 

Sa-li'va  (Lat.  saliva;  Gr.  sialon,  spittle),  the  watery  fluid  in  the 
mouth. 


420  GLOSSARY 

Sa-pon-i-fi-ca'tion  (Lat.  sapo,  soap,  and  facer e.  to  make),  the  process 
of  making  soap.  Commonly  the  name  soap  is  applied  only  to  the 
combination  of  soda  or  potash  with  the  acid  part  of  fat.  But  lime, 
or  magnesium,  or  other  metal  may  take  the  place  of  soda  or  potash, 
as  it  does  when  hard  water  and  soap  are  used  to  wash  the  hands. 
The  lime  soap  which  is  formed  feels  sticky  and  rough,  and  does  not 
dissolve  in  water,  but  forms  a  white  scum  on  the  surface. 

Scap-u-la  (Lat.  scapulae^  the  shoulder  blades),  the  flat  bone  upon  the 
back  behind  the  shoulder.     The  shoulder  blade. 

Sciatica  {si-af  i-ka)  (Gr.  ischiadikos,  pertaining  to  the  hip),  a  painful 
inflammation  of  the  main  nerve  of  the  leg  which  begins  just  behind 
the  hip  joint. 

Sclerotic  {skler-ot'ic)  (Gr.  skleros,  hard),  the  tough  outer  covering  of 
the  eyeball. 

Scur'vy,  the  disease  caused  by  lack  of  variety  of  food.  It  consists  of 
pain  and  of  bleeding  under  the  skin,  especially  of  the  legs  and  gums. 

Sebaceous  glands  {se-ba' shus)  (Lat.  sebum,  fat),  the  glands  in  the  skin 
which  secrete  oil. 

Se-cre'tion  (Lat.  secretus,  separated),  a  substance  which  is  separated 
from  the  blood  by  the  epithelium  of  glands  and  used  by  the  body. 

Sem-i-cir'cu-lar  canals,  the  three  tunnels  in  the  inner  ear  in  which  there 
are  nerves  whose  duty  is  to  take  note  of  the  position  of  the  body  in 
balancing  itself. 

Sem-i-lu'nar  valves,  three  half-moon-shaped  valves  at  the  beginning 
both  of  the  aorta  and  of  the  pulmonary  artery.  They  prevent  blood 
from  flowing  back  to  the  heart. 

Sen-sa'tion  (Lat.  sentire,  to  feel),  a  conscious  impression  made  upon 
the  brain  by  an  impulse  brought  by  a  sensory  nerve. 

Sen'so-ry  nerves  (Lat.  sentire,  to  feel),  nerves  which  carry  impulses 
from  the  cells  to  the  central  nervous  system. 

Se'rous  membrane,  the  thin  membrane  lining  the  cavities  of  the  body 
which  do  not  connect  with  its  surface.  It  is  named  from  the  fluid, 
like  serum,  which  forms  in  it  in  a  quantity  just  sufficient  for  lubri- 
cation. 

Se'rum  (Lat.  sernin^  the  watery  part  of  curdled  milk),  the  straw-colored 
liquid  which  separates  from  a  blood  clot. 

Sewer  (sii'er),  an  underground  tunnel  for  carrying  slops  from  the  houses 
of  a  town. 

Si'nus  (Lat.  sinus,  curve),  a  cavity. 


GLOSSARY  42 1 

Skel'e-ton  (Gr.  skellein,  to  dry),  the  bones  of  the  body. 
So-lu'tion  (Lat.  solittiis^  dissolved),  a  hquid  mixture  in  which  the  in- 
gredients are  not  changed  in  essential  properties. 
Speech,  the  expression  of  thoughts  by  words. 
Spine  (Lat.  spina,  the  backbone),  the  backbone. 
Spleen  (Gr.  spien),  a  soft,  red  organ  lying  to  the  left  of  the  stomach. 

Its  use  is  probably  co  form  the  red  blood  cells. 
Spore  (Gr.  spora,  seed),  a  reproductive  cell  of  a  fiowerless  plant.     Spores 

are  extremely  minute,  and  some  are  capable  of  resisting  influences 

which  are  fatal  to  most  other  forms  of  life. 
Stapes  (Lat.  stapes,  stirrup),  the  third  bone  in  the  chain  of  bones  which 

conducts  sound  from  the  membrana  tympani  to  the  inner  ear. 
Starch  (Anglo-Saxon,  siearc,  strong),  a  food  substance  composed  of 

carbon,  hydrogen,  and  oxygen.     It  is  the  first  recognizable  form 

through  which  organic  substances  pass  as  they  are  built  up  by  plants. 

In  the  body  it  is  changed  to  sugar. 
Ste-ap'sin  (Gr.  stear,  suet),  the  ferment  of  the  pancreatic  juice  which 

digests  fat. 
Ster'il-ize  (Lat.  sterilis,  without  power  to  produce  seed),  to  destroy 

bacteria  and  their  spores  as  by  heat  or  chemicals.      It  is  usually 

applied  to  the  preparation  of  surgical  dressings. 
Ster'num  (Gr.  sternon,  the  breast),  the  flat  bone  which  extends  down 

the  front  of  the  breast ;  the  breast  bone. 
Stim'u-lant  (Lat.  stimulus,  a  whip),  a  substance  which  excites  a  part 

to  action  without  increasing  its  supply  of  energy. 
Stomach  {stmn'ak)  (Gr.  stoma,  a  mouth  or  entrance),  the  muscular 

bag  into  which  food  enters  when  swallowed,  and  which  begins  the 

work  of  digestion. 
Strych'nine  (Gr.  struchjios,  a  kind  of  shrub),  a  substance  obtained  from 

the  seeds  of  the  strychnos  shrub.    It  is  used  to  increase  the  power  of 

the  nervous  system  ;  in  overdoses  it  produces  violent  convulsions. 
Sub-lin'gual  glands  (Lat.  sub,  under,  and  lingua,  tongue),  the   two 

salivary  glands  under  the  front  part  of  the  tongue. 
Sub-max'il-la-ry    gland    (Lat.    sub,    under,    and    maxilla,  jaw),    the 

salivary  gland  situated  under  the  side  of  the  lower  jaw. 
Su'gar  (Lat.  saccharum,  sugar),  a  sweet  substance  composed  of  carbon, 

hydrogen,  and  oxygen  in  nearly  the  same  proportions  as  in  starch. 

There  are  many  varieties,  but  during  digestion  all  are  changed  to 

glucose  or  grape  sugar.     It  gives  heat  to  the  body. 


422  GLOSSARY 

Syrvi-an  fissure,  the  deep  fissure  extending  backward  upon  each  side 

of  the  brain.     It  was  named  after  the  French  physician  Sylvius,  who 

died  in  1555. 
Sym-pa-thet'ic  system,  the  collection  of  nervx  cells  and  nerves  which 

control  the  preparation  of  food  and  its  distribution  to  the  cells.     It 

is  subordinate  to  the  spinal  cord. 
Syn-o'vi-a,  the  fluid  which  lubricates  the  movable  joints. 
Syn-o'vi-al  membrane,  the  membrane  lining  the  movable  joints. 
Sys'tem  (Gr.  siifiistanai,  to  place  together),  a  series  of  tissues  and 

organs,  working  together  for  a  definite  purpose. 
Sys'to-le  (Gr.  swt^  together,  and  stelleifi,  to  set),  the  contraction  of 

the  heart  forcing  blood  into  the  arteries  of  the  body. 

Tan'nin  (Fr.  tan^  originally  meaning  oak),  an  acid  found  in  the  barks 
of  most  trees,  and  used  to  toughen  and  harden  skins  into  leather. 

Tape  worm,  a  kind  of  worm  inhabiting  the  intestine.  It  resembles  a 
long  piece  of  white  tape. 

Tar'sal  bones  (Gr.  tarsos,  the  sole  of  the  foot),  the  eight  irregularly 
shaped  bones  in  the  hinder  half  of  the  foot. 

Tar'tar,  a  kind  of  hard,  brown  substance  which  often  forms  upon  the  teeth. 

Tau-ro-chol'ic  acid,  one  of  the  waste  substances  in  the  bile. 

Tem'po-ral  (Lat.  tempora,  the  temples),  pertaining  to  the  regions  of 
the  skull  in  the  neighborhood  of  the  ears. 

Ten'don  (Lat.  tendere,  to  stretch),  a  strong  white  cord,  one  end  of 
which  is  attached  to  a  muscle  above  a  joint,  and  the  other  to  a  bone 
or  to  flesh  below  a  joint. 

Thoracic  duct,  the  tube  running  upward  upon  the  backbone  and  con- 
veying lymph  to  the  veins. 

Tho'rax  (Gr.  thorax,  breastplate),  the  cavity  of  the  body  under  the 
ribs. 

Thy'roid  (Gr.  thnreos,  a  shield,  and  eidos,  form).  The  large  folded 
cartilage  which  forms  the  principal  part  of  the  larynx. 

Tib'i-a  (Lat.  tibia),  the  shin  bone. 

Tissue  {ti'shii),  a  group  of  cells  or  fibers  alike  in  form  and  action. 

To-bac'co  (West  Indian  tabaco,  the  name  of  the  pipe  used  in  smoking), 
a  narcotic  plant  used  for  smoking  and  for  chewing. 

Ton'sil  (Lat.  toiisilla),  3.  round  body  situated  one  on  each  side  of  the 
throat  in  front  of  the  pharynx.  They  have  no  special  use.  Some- 
times they  become  enlarged,  and  need  to  be  removed. 


GLOSSARY  423 

Tox'in  (Gr.  toxikon,  arrow  poison),  a  virulent  poison  formed  within  a 
living  body.     Most  toxins  are  ptomaines. 

Tra'che-a  (Gr.  trachus,  rough),  the  windpipe;  rings  of  cartilage  make 
its  outside  irregular  and  rough. 

Trans-fu'sion  (Lat.  trans,  across,  2in6.fu7idere,  to  pour  out),  transferring 
blood  from  the  veins  of  one  person  into  the  veins  of  another. 

Tri'ceps  (Lat.  tri,  three,  and  caput,  head),  the  muscle  extending  down 
the  back  of  the  arm  from  the  shoulder  to  the  elbow.  It  straightens 
the  elbow.     Its  upper  end  has  three  branches. 

Trichinae  {trick-i' nee)  (Gr.  thrix,  a  hair),  microscopic  worms  which 
live  in  the  muscles  of  a  pig.  They  sometimes  remain  alive  in  par- 
tially cooked  pork,  and  if  eaten  produce  a  deadly  disease. 

Tri-cus'pid  valve  (Lat.  tres,  three,  and  ciispis,  point),  the  valve  between 
the  right  auricle  and  ventricle  ;  it  is  formed  of  three  leaves. 

Tryp-sin  (Gr.  tribeiji,  to  rub),  the  ferment  of  the  pancreatic  juice  which 
digests  albumin. 

Tu-ber-cu-lo'sis  (Lat.  tuberculum,  a  little  lump),  a  disease  in  which 
small  white  lumps  like  pinheads  form  in  the  flesh.  Later,  these 
soften  and  run  out  as  matter.  The  disease  is  commonly  called  con- 
sumption. 

Tym'pa-num  (Lat.  tympanutn,  drum),  the  middle  ear. 

Ty'phoid  fever  (Gr.  tuphos,  a  cloud,  and  hence  a  stupor  arising  from 
fever,  and  eidos,  form),  a  tedious  and  weakening  fever  caused  by  the 
growth  of  a  kind  of  bacteria. 

Ty-ro-tox'i-con  (Gr.  tiiros,  cheese,  and  toxicon,  poison),  a  virulent 
ptomaine  poison  sometimes  found  in  cheese  and  other  substances 
made  from  milk. 

Ul'na  (Lat.  ulna,  the  elbow),  the  bone  on  the  little  finger  side  of  the 

lower  arm. 
U're-a    (Gr.  our  on,  urine),  a  very  soluble  crystalline  substance,  one  of 

the  three  principal  waste  products  of  the  body.     It  is  the  essential 

part  of  urine. 
U-re'ter  (Gr.  ouron,  urine),  the  tube  leading  from  the  kidney  to  the 

bladder. 

Vac-cin-a'tion  (Lat.  vacca,  a  cow),  the  introduction  of  the  germs  of 
cowpox  into  the  skin  for  the  purpose  of  causing  the  disease  as  a 
protection  against  smallpox. 


424  GLOSSARY 

Valv'u-lae  con-ni-ven'tes  (Lat.  valvidae,  little  sliding  doors,  and  conni- 
ventes,  winking),  deep  puckers  in  the  mucous  membrane  of  the 
small  intestine. 

Var'i-cose  veins  (Lat.  varix,  an  enlarged  vein),  distended  and  enlarged 
veins. 

Vas-0-mo'tor  nerves  (Lat.  vasa,  a  vessel,  and  jnotor,  pertaining  to 
motion),  nerves  which  produce  either  contraction  or  dilatation  of  the 
arteries. 

Vein  {vane)  (Lat.  vena,  a  vein),  a  tube  which  carries  blood  back  to 
the  heart. 

Ven-ti-la'tion  (Lat.  ventilare,  to  winnow),  changing  the  air  of  a  room. 

Ven'tri-cle  (Lat.  ventriculus,  stomach),  one  of  the  large,  thick-walled 
cavities  of  the  heart. 

Ven-tril'o-quism  (Lat.  venter,  the  abdomen,  and  logui,  to  speak), 
speaking  so  that  the  voice  seems  to  come  from  a  distance  away 
from  the  speaker. 

Ver'mi-form  ap-pen'dix  (Lat.  ver?ms,  worm,  appendix,  something 
added),  the  closed  tube,  shaped  like  an  earthworm,  which  projects 
from  the  beginning  of  the  large  intestine.  In  some  of  the  lower 
animals,  as  in  the  hen,  it  is  as  large  as  the  other  part  of  the  intes- 
tine, but  in  man  is  only  about  two  inches  in  length  and  one  eighth 
inch  in  diameter. 

Ver'te-bra  (Lat.  vertebra),  a  joint  of  the  backbone. 

Vest'i-bule  (Lat.  vestibidum,  a  porch  or  entrance),  the  cavity  of  the 
internal  ear  from  which  the  cochlea  and  semicircular  canals  extend. 

Villus  (Lat.  villus,  a  tuft  of  hair),  one  of  the  minute  slender  projections 
upon  the  inner  surface  of  the  intestine. 

Vin'e-gar,  a  sour  liquid  made  from  wine  or  cider  by  the  oxidation  of  its 
alcohol  to  acetic  acid,  of  which  it  contains  from  two  to  four  per  cent. 

Vit're-ous  hu'mor  (Lat.  vitrian,  glass),  the  jelly-like  fluid  which  fills 
the  eyeball  behind  the  lens. 

X  rays,  a  form  of  radiant  energy  discovered  by  Roentgen  in  1895.  It 
penetrates  wood,  flesh,  and  many  other  substances  which  are  opaque 
to  sunlight. 

Yeast,  a  collection  of  single-celled  plants,  whose  growth  changes  sugar 
to  alcohol  and  carbonic  acid  gas.  The  agent  which  causes  bread  to 
become  light. 


INDEX 


Abdomen,  66. 
Abscess,  395. 
Absorption,  89,  260. 
Accommodation,  339. 
Achilles'  tendon,  374. 
Acid,  28,  149. 
Aconite,  148,  15 1. 
Adam's  apple,  349. 
Adenoid  vegetations,  193,  327. 
Adulteration,  of  alcohol,  47. 
of  coffee,  127. 
of  milk.  III. 
Air,  206,  220. 
in  lungs,  207. 
in  clothing,  238. 
moisture  in,  236. 
rarefied,  222. 
sacs,  195. 
Albumin,  23,  34,  69,  84,  92. 
Alcohol,  44,  140. 

effects  on  arteries,  189. 

brain,  315. 

digestion,  98. 

excretion,  251. 

habit,  319. 

heart,  168. 

heat,  243. 

heredity,  319. 

intestine,  100. 

judgment,  316. 

kidney,  251. 

liver,  ICXD. 

lungs,  213. 

muscle,  377. 

nerves,  273. 

paralysis,  317. 

peristalsis,  99. 

respiration,  214. 

sight,  342. 

stomach,  99. 

voice,  354. 


Alimentary  canal,  53. 
Alkalies,  28,  149. 
Alkaloids,  152. 
Ameba,  10. 
Amylopsin,  84. 
Anaesthesia,  146,  223,  320. 
Anatomy,  9. 
Anemia,  159. 
Antidote,  149. 
Antimony,  151. 
Antiseptics,  387. 
Antitoxin,  386. 
Antrum,  54,  193,  324. 
Aorta,  172, 
Apoplexy,  311. 
Appendicitis,  80. 
Appendix,  vermiform,  80. 
Appetite,  74. 
Aqueous  humor,  334. 
Argon,  220. 
Arsenic,  150. 

iVrterial  blood,  157,  177,  207. 
Artery,  163,  172,  187. 
Asphyxia,  212. 
Assimilation,  91. 
Astigmatism,  340. 
Auricle,  163. 

Bacteria,  384. 
Barley,  122. 
Bathing,  261. 
Beans,  122. 
Beard,  261. 
Beds,  240. 
Beef  tea,  115. 
Beer,  43. 
Belladonna,  152. 
Biceps,  375. 
Bicuspid  tooth,  55. 
Bile,  84,  85,  93. 
Biliousness,  85,  93. 


425 


426 


INDEX 


Bilirubin,  250. 
Biscuit,  121. 
Bitters,  loi. 
Blackheads,  259. 
Bladder,  84,  249. 
Bleeding,  186. 
Blister,  257. 
Blood,  156,  206, 

as  food,  117. 

in  lower  animals,  159. 

poisoning,  389. 
Blowing,  198. 
Boards  of  health,  389. 
Bones,  357. 

Bowels,  regularity  of,  94. 
Brain,  289. 

food,  133,  309. 

in  lower  animals,  300. 
Bread,  43,  121,  122. 
Breathing,  192,  198. 
Bright's  disease,  249. 
Broken,  back,  281. 

bones,  361. 
Bronchi,  195. 
Bunion,  366. 
Burns,  242. 
Butter,  III. 
Butterine,  1 1 2. 

Caecum,  80. 

Caisson,  222. 

Cake,  121. 

Callus,  257. 

Cancellous  bone,  359. 

Canine  teeth,  54. 

Cannabis  indica,  145, 

Canned  food,  42,  125. 

Capillary,  173,  208. 

Carbolic  acid,  150,  388, 

Carbon,  33,  36. 

Carbonic  acid  gas,  33,  206,  208,  223. 

Cardiac,  67. 

Carpal  bones,  358. 

Cartilage,  360. 

Caseine,  109. 

Cataract,  340. 

Catarrh,  61. 

Cellar  air,  224. 

Cells,  II,  13,  92,  174,  393. 

Cellulose,  26. 

Cement,  55. 

Cerebellum,  292. 


Cerebrum,  293. 
Cesspool,  252. 
Cheeks,  56. 
Cheese,  no. 
Chemical  action,  28. 
Chicory,  127. 
Chill,  234. 
Chloral,  145. 
Chloride  of  lime,  388. 
Chloroform,  146,  320. 
Chlorophyll,  35. 
Choking,  199. 
Cholera,  385. 
Choroid  coat,  334. 
Chyle,  86. 
Chyme,  69. 
Cigar,  141. 
Cigarette,  142. 
Cilia,  195,  197,  205,  218. 
Circulation,  177. 

in  lower  animals,  1 80. 
Clabber,  no. 
Clams,  116. 
Clavicle,  358. 
Clothing,  237. 
Clot,  158. 
Coagulation,  23. 
Coal  gas,  225. 

Cocaine,  145. 

Coccyx,  357. 

Cochlea,  326. 

Cocoa,  127. 

Coffee,  126. 

Cold,  sensation  of,  234, 
feet,  239. 
taking,  185,  396. 

Colon,  80, 

Color,  blindness,  337. 
and  heat,  238. 
of  skin,  257. 

Complexion,  259. 

Condensed  milk,  1 12. 

Congestion,  185,  393. 

Conjunctiva,  336. 

Connective  tissue,  11,  38,  394. 

Conservation  of  energy,  36. 

Consonants,  352. 

Consumption,  see  Tuberculosis. 

Contagious  diseases,  385. 

Contraction  of  muscles,  373. 

Convolutions  of  brain,  293. 

Cooking,  51,  123. 


INDEX 


427 


Copper,  150. 
Corn  meal,  122. 
Cornea,  335. 
Corns,  257. 
Corpuscles,  156. 
Cotton,  237. 
Coughing,  198. 
Crabs,  117. 
Cranial  nerves,  290. 
Cricoid  cartilage,  349. 
Crown  of  tooth,  55. 
Crying,  198. 
Cud,  104. 

Curvature  of  spine,  366. 
Cuticle,  257. 
Cutis,  256. 

Deafness,  327, 
Decay,  13,  24,  42,  46,  384. 
Decayed  food,  152. 
Deglutition,  61. 
Delirium,  311. 

tremens,  318. 
Dentine,  55. 
Derma,  256. 
Diaphragm,  66,  196. 
Diastole  of  heart,  165. 
Diet  list,  132. 
Diffusion,  24. 
Digestibility  of  food,  108. 
Digestion,  51. 

in  lower  animals,  104. 
Diphtheria,  385. 
Disease,  148. 

of  bone,  361. 

of  eye,  341. 

of  heart,  167. 

of  hip  joint,  368. 

of  spine,  281. 

germs,  226,  385. 
Dislocations,  367. 
Distillation,  44. 
Dreams,  308. 
Dropsy,  180. 
Drowning,  213. 
Drugs,  148. 
Duodenum,  80. 
Dura  mater,  290. 
Dust,  221, 
Dyspepsia,  74,  93. 

Ear,  325. 
wax,  329. 


Ear,  in  lower  animals,  329. 
Eating,  76,  132. 
Eggs,  112. 
Electric  shock,  213. 
Emergencies  — 

Alcoholic  paralysis,  141,  317. 

Apoplexy,  311. 

Asphyxia,  212. 

Bleeding,  186. 

Broken  bones,  361. 

Burns,  242. 

Choking,  199. 

Coal  gas,  225. 

Cold,  taking,  185. 

Contagious  diseases,  385. 

Dislocation  of  bones,  367. 

Drowning,  213. 

Electric  shock,  213. 

Fainting,  150,  168. 

Fever,  233,  242,  263. 

Fits,  312. 

Fright,  312. 

Frozen  limbs,  241. 

Hysteria,  309. 

Insanity,  310. 

Panics,  312. 

Poisoning,  144,  149. 

Sprains  of  joints,  367. 

Stings,  154. 

Sunstroke,  236. 
Emulsion,  25. 
Enamel,  55. 
Energy,  conservation  of,  36. 

source  of,  233. 
Epidermis,  257. 
Epiglottis,  61. 
Epilepsy,  312, 
Epithelium,  57,  58,  68,  82,  248,  257, 

261,  271,  394. 
Erysipelas,  385,  389. 
Esophagus,  62. 
Ether,  320. 

Eustachian  tube,  327. 
Excretion,  248. 
Exercise,  166,  309,  377. 
Exhaustion  of  retina,  337. 
Expansion  of  lung,  197. 
Expiration,  196. 
Extensor  muscles,  375. 
Eye,  334. 

in  lower  animals,  344. 
Eyelids,  336. 


428 


INDEX 


Face,  376. 
Fainting,  150,  168. 
Far  sight,  339. 
Fat,  25,  34,  91.  209. 
Fatty  heart,  167. 
Femur,  358. 

Fermentation,  42,  76,  lOO,  109. 
Fever,  233,  242,  263. 
Fibrin,  158. 
Fibula,  359. 
Field  of  view,  337. 
Filtration,  137. 
of  air,  229. 
Fissures  of  brain,  293. 
Fish,  116. 
Fits,  312. 
Flat  foot,  359. 
Flexor  muscles,  375. 
Fluids  of  body,  15. 
Focus,  18. 

Food,  51,  107,  120,  131. 
Foul  air,  223. 
Freckles,  257. 
Frontal  region,  294. 
Frozen  limbs,  241. 
Fruit,  124. 
Fulcrum,  373. 
Fur,  238. 
Fusel  oil,  45. 

Gall  bladder,  84. 

Ganglia,  284. 

Gaping,  198. 

Gastric  juice,  68. 

Gelatine,  23. 

Germs,  no,  384. 

Gills,  216. 

Gizzard,  105. 

Gland,  57. 

Glucose,  51,  92. 

Glue,  23. 

Gluten,  120. 

Glycocholic  acid,  250. 

Glycogen,  92. 

Goose  flesh,  259. 

Gout,  367. 

Grain,  120. 

Gray  matter,  276,  290,  292,  293. 

Grippe,  385. 

Habit,  142,  306. 
Hair,  259. 
Hangnail,  261, 


Hasheesh,  145. 

Haversian  canals,  360. 

Headache,  95,  340. 

Heart,  162. 

Heat,  34,  233. 

Hemoglobin,  24,  156,  207. 

Hemophilia,  159. 

Hemorrhage,  186. 

Heredity,  306. 

Hibernation,  243. 

Hiccough,  198. 

Hip,  358. 

Hip  joint  disease,  368. 

History  of  circulation,  181. 

Humerus,  358. 

Humors,  159. 

Hunchback,  368. 

Hunger,  269. 

Hydrochloric  acid,  68. 

Hydrogen,  33. 

Hygiene,  9. 

Hypodermic  injections,  153,  180. 

Hysteria,  309. 

Ileum,  80. 

Illusions,  of  hearing,  329. 

of  sight,  342. 
Incisor,  54. 
Incus,  326. 
Indigestion,  73,  93. 
Infectious  diseases,  385. 
Inflammation,  393. 
Ingrowing  nail,  261. 
Insalivation,  53. 
Insanity,  310. 
Inspiration,  196. 
Instincts,  268. 
Intellect,  299. 

Intemperance  in  eating,  75,  lOI,  251. 
Intensity  of  voice,  351. 
Intestinal  juice,  84. 
Intestine,  79. 
Intoxication,  214,  317. 
Iris,  335. 
Iron,  24,  124. 
Itching,  271. 
Ivory,  55. 

Jaundice,  250. 
Jaws,  54. 
Jejunum,  80. 
Joints,  364. 


INDEX 


429 


Kidneys,  249. 

Labyrinth,  325. 
Lachrymal  gland,  336. 
Lacing,  tight,  200. 
Lacteal,  91. 
Lactometer,  iii. 
Larynx,  194,  349. 
Laudanum,  144. 
Laughing,  198. 
Lead,  136,  150. 
Lens,  s^. 
Leucomaines,  152. 
Levers,  373. 
Life,  9,  12,  sS,  398. 
Ligaments,  365. 
Light,  333. 
Lime,  28. 
Lips,  56. 

Liver,  82,  93,  250. 
Living  rooms,  236. 
Lobsters,  117. 
Lungs,  192. 
Lymph,  178. 
Lymphatics,  174,  178. 
Lymph  nodes,  178. 

Malaria,  225. 
Malleus,  126. 
Malt,  43. 
Mania,  310. 
Marrow,  160,  359. 
Mastication,  60. 
Mastoid,  327. 
Meat,  113. 

Medulla  oblongata,  290. 
Melancholia,  311. 
Membrane,  327. 
Memory,  295,  297. 
Mercury,  150,  388. 
Mesentery,  79. 
Metacarpal  bones,  358. 
Metals,  150. 
Metatarsal  bones,  359. 
Microbes,  384. 
Microscope,  16. 
Milk,  109. 

Mind,  stimulation  of,  305. 
Minerals,  27,  33,  51. 
Mitral  valve,  164. 
Molar  teeth,  55. 
Mold,  383. 


Morphine,  144. 
Motor,  region,  296. 

center,  278,  296. 

nerves,  271. 
Mouth,  53. 

breathing,  193,  353. 
Mucous  membrane,  57, 
MuUer's  fluid,  72. 
Muriatic  acid,  363. 
Muscles,  366,  371,  376. 
Muscular  sense,  271. 
Mushroom,  152. 

Nails,  259. 
Narcotics,  140,  150. 
Nasal  duct,  336. 
Near  sight,  339. 
Nerve  cells,  276. 
Nerves,  266. 

of  heart,  166. 

motor,  271. 

sensory,  268. 

sympathetic,  285. 
Nervousness,  309. 
Neuritis,  273. 
Neutralize,  28. 
Nicotine,  141. 
Night  air,  225. 
Nose,  192,  324. 
Nucleo-album.in,  24,  126. 
Nucleus,  II,  12,  24. 
Nuts,  125. 

Oatmeal,  122. 
Occipital  region,  295. 
Occupation  diseases,  221. 
Odors,  224. 
Oleomargarine,  112. 
Olfactory  nerves,  325. 
Omentum,  80. 
Opium,  143,  320. 
Optic,  nerve,  334. 
tubercles,  292. 
Orbit,  336. 

Organic  substances,  37. 
Organs,  16. 

Oxidation,  33,  46,  209,  233,  243. 
Oxygen,  33,  131,  207,  212,  221. 
Oysters,  116. 
Ozone,  220. 

Pain,  270. 
Palate,  53. 


430 


INDEX 


Palpitation  of  heart,  i66,  167. 

Pancakes,  121. 

Pancreas,  82. 

Pancreatic  juice,  84. 

Panics,  312. 

Paper  clothing,  239. 

Papilla,  258, 

Paralysis,  272. 

Paregoric,  144. 

Parietal  region,  294. 

Parotid  gland,  59. 

Patella,  359,  375- 

Paunch,  104. 

Peas,  122. 

Pelvis,  358. 

Pepsin,  69. 

Peptone,  24,  69,  92. 

Pericardium,  162. 

Periosteum,  359,  360. 

Peristalsis,  63,  69,  85. 

Peritoneum,  66. 

Perspiration,  235,  248.    . 

Phalanges,  359. 

Pharynx,  61,  193. 

Phosphorus,  151. 

Physiology,  9. 

Pia  mater,  290. 

Pitch  of  voice,  350. 

Plants  and  animals,  37. 

Plasma,  157. 

Play,  378. 

Pleura,  196. 

Plexus,  285. 

Plumbing,  253. 

Pneumogastric  nerve,  291. 

Pneumonia,  397. 

Poisoning,  149. 

Portal,  circulation,  177. 

vein,  92. 
Potash,  28. 
Potatoes,  122. 
Poultice,  396. 
Protoplasm,  1 1. 
Proud  flesh,  258,  394. 
Proximate  principles,  22. 
Ptomaines,  153,  384. 
Ptyalin,  59. 

Pulmonary  circulation,  176. 
Pulse,  173. 

Pupil,  335- 

Purification  of  air,  230. 
Pus,  395. 


Putrefaction,  see  Decay. 
Pylorus,  67. 
Pyridine,  142. 

Quality  of  voice,  351. 

Radius,  358. 

Reaction  of  bath,  262. 

Reconstruction  after  oxidation,  35. 

Red  blood  cells,  157. 

Reflex  action,  278. 

Regions  of  brain,  294. 

Rennin,  69. 

Repair,  of  injuries,  393. 

in  blood  tubes,  188. 

in  nerves,  273. 
Respiration,  175,  192,  208,  217. 

artificial,  202. 

in  lower  animals,  215. 
Respiratory  center,  201,  21 1,  291, 
Retina,  334. 
Rheumatism,  367. 
Ribs,  357.      . 
Rice,  122. 
Rickets,  361. 
Ringworm,  384. 
Root  beer,  48. 
Round  shoulders,  377. 
Rumen,  104. 

Sacrum,  357. 
Saliva,  59. 
Salt,  27. 

Saponification,  26,  85. 
Scapula,  358. 
Scar,  394. 
Sciatica,  273. 
Sclerotic  coat,  334. 
Scrofula,  179. 
Scurvy,  126. 
Seasonings,  126. 
Sebaceous  glands,  259. 
Secretion,  58,  272. 
Semicircular  canals,  326. 
Semilunar  valve,  164. 
Sensation,  268. 
Sensibilities,  299. 
Sensory  regions,  295. 
Serous  membrane,  67. 
Serum,  158. 
Sewage,  251. 
Sewer,  252.     ■ 


INDEX 


431 


Sewer  gas,  224,  252. 

Shortness  of  breath,  21 1. 

Sick  room,  388. 

Sighing,  199. 

Sight,  335. 

Silk,  238. 

Silver,  150. 

Sinus,  324. 

Site  for  house,  253. 

Skeleton,  357. 

Skin,  256. 

grafting,  258. 
Sleep,  307. 
Smell,  325. 
Smoking,  141. 
Smothering,  199. 
Snake  bites,  153. 
Sneezing,  198. 
Snoring,  198. 
Snuff,  142. 
Soap,  26. 
Sobbing,  198. 
Soda,  28. 
Solar  plexus,  285. 
Solution,  22. 
Sounds,  of  heart,  166. 
of  breathing,  198. 
Soup,  115. 

Specimens,  19,  72. 

Speech,  297,  351. 

Spinal,  column,  357. 
cord,  276. 
nerves,  277. 

Spitting,  199. 

Spleen,  160. 

Spores,  383. 

Sprains,  367. 

Standing,  375. 

Stapes,  326. 

Starch,  26,  35,  84. 

Starvation,  133. 

Steapsin,  85. 

Sterilization,  387. 

Sternum,  357. 

Stimulants,  126,  168. 

Stings,  154. 

Stomach,  67. 

Strychnine,  150. 

Subcutaneous  tissue,  256. 

Sublingual  gland,  59. 

Submaxillary  gland,  59. 

Sucking,  199. 


Suffocation,  199. 
Sugar,  26,  35,  132,  209. 
Summer  complaint,  no. 
Sun  in  plant  growth,  36. 
Sunstroke,  236. 
Swallowing,  62. 
Sylvian  fissure,  293. 
Sympathetic  system,  284. 
Synovial  membrane,  365. 
Systems,  16. 
Systole  of  heart,  165. 

Tannin,  127. 
Tapeworm,  117. 
Tarsal  bones,  359. 
Tartar,  56. 
Taste,  74,  323-. 
Taurocholic  acid,  250. 
Tea,  126. 
Tears,  336. 
Teeth,  54. 

Temperance  drinks,  48. 
Temperature,  of  body,  233. 
in  lower  animals,  243. 
sense,  234,  270. 
Temporal  region,  294. 
Tendon,  372. 
Thirst,  47,  269. 
Thoracic  duct,  91,  179. 
Thorax,  196. 
Thought  regions,  297. 
Thyroid  cartilage,  349. 
Tibia,  359. 
Tickling,  271. 
Tissues,  14. 
Tobacco,  141. 

effects  on  brain,  319. 

heart,  169. 

lungs,  215. 

sight,  342. 

smell,  325. 

voice,  353. 
Tongue,  57,  352. 
Tonsil,  193. 
Touch,  269,  323. 
Toxins,  384. 
Trachea,  194. 
Triceps,  375. 
Trichinae,  117. 
Tricuspid  valve,  164. 
Trvpsin,  84. 
Tuberculosis,  117,  226,  368,  389. 


432 


INDEX 


Tusk,  55. 
Tympanum,  327. 
Typhoid  fever,  no,  385. 
Tyrotoxicon,  153. 

Ulna,  358. 

Unconscious  mind  action,  307. 

Urea,  34,  248. 

Ureter,  249. 

Urine,  249. 

Vaccination,  387. 
Vagus  nerve,  291. 
Valves  of  heart,  164. 
Valvulse  conniventes,  81. 
Varicose  veins,  189. 
Vasomotor,  center,  291. 

nerves,  185. 
Vegetables,  124. 
Veins,  163,  175. 
Venous  blood,  157,  177,  20 
Ventilation,  226. 
Ventricle,  of  brain,  294. 

of  heart,  163. 
Ventriloquism,  341. 


Vermiform  appendix,  80. 
Vertebra,  357. 
Vestibule,  325. 
Villi,  81. 
Vinegar,  41, 
Vitreous  humor,  334. 
Vocal  cords,  350. 
exercise,  353. 
Voice,  194,  349. 
Vowels,  352. 

Walking,  376. 

Wart,  258. 

Water,  22,  33,  135. 

White  blood  cells,  157,  174,  386,  393. 

matter,  276,  290,  293. 

svv^elling,  368. 
Will,  299. 
Wine,  44. 
Wood,  26,  38. 
Wool,  237. 


X  rays,  342. 

Yawning,  198. 
Yeast,  41,  382. 


GiP3^ 


OvZ 


